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Study Methodology of Analytical Group II Cations
Chanturia Mineda
PhD, Associate Professor, Doctor of Chemistry, Faculty of Natural Science, Mathematics, Technology
and Pharmacy, Sokhumi State University
DOI: https://dx.doi.org/10.51584/IJRIAS.2025.1010000096
Received: 10 October 2025; Accepted: 15 October 2025; Published: 10 November 2025
ABSTRACT
The article analyzes properties, significance and application of metal cations of the II analytical group
,
, formed on the basis of many years of experience in teaching chemistry. Principles with the
following stages: base-acid classification of II analytical group cations: General characterization of cations of
analytical group II with base-acid classification → Chemical bases of toxic action of their representative heavy
metals - integration with ecology → Their importance and use in medicine - integration with medicine,
solving the tasks of the teaching process of human life safety → Private reactions of identification - solving
the tasks of the teaching process of chemistry → Control task: the course of analysis of II analytical group of
cations in the course of systematic analysis → drawing up the results of private reactions and mixture analysis
of II analytical group according to the given schemes → Laboratory work assessment system → Synthesis of
information - multi-component analysis of the studied material.
INTRODUCTION
Teaching the course “Analytical Chemistry” focuses on mastering modern and classical chemical analysis
methods. It also addresses theoretical problems, develops new techniques for component identification and
quantification, and improves existing methods to determine chemical composition.
The concept of teaching analytical chemistry has been elaborated and thoroughly defined, the base and
foundation of which is the lecture theoretical material. The theory formulates laws using scientific concepts,
terms, and hypotheses. At the lectures, The course introduces students to the essence of the course, its purpose,
tasks, main content, final result, and simple and acceptable ways to achieve them.
Relevance of the topic:
In the literature, various ion detection, identification-classification systems are known: sulphide, base-acid,
phosphate-ammonia, etc. The sulphide method of analysis is classical. Its theory and practice are well studied
and worked out, although toxic hydrogen sulfide is used in its work. At Sukhumi State University, preference
was given to the environmentally safe base-acid method of classification of cations and anions, which greatly
contributes to the formation of the student's logical, analytical thinking, which is the strongest tool for physical,
moral and spiritual perception of the world.
The base-acid system of cation analysis divides metal cations into six groups. This classification depends on
their reactions with hydrochloric acid, sulfuric acid, alkalis, and ammonia solutions. [1]
The positive side of the system is as follows: basic properties of elements are used in the basic-acid system of
analysis: their dependence on acids and alkalis, amphotericity of hydroxides and the ability to form complexes
of elements. The batch reagent needs to satisfy these requirements:
1. Precipitation of cations should be practically quantitative (the concentration of cations in the solution
after precipitation should not exceed
g-ion/l);
2. The resulting precipitate should be easily dissolved in acids for further analysis;
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3. The excess amount of reagent added should not interfere with the identification of ions remaining in
solution.
The paper discusses the main principles of analysis, properties, importance and use of metal cations of the II
analytical group
,
, formed on the basis of many years of experience in teaching chemistry,
as follows in stages:
Table #1
I
General characterization of cations of analytical group II with base-acid classification.
II
Chemical bases of the toxic effect of heavy metals representative of analytical group II - [Evaluation of the
importance of elements in human life and production from the point of view of their use (Chemistry, Natural
Sciences.4,12,13)]. Integration with ecology.
III
Their importance and use in medicine. Integration with medicine, solving the tasks of the process of
teaching the safety of human life.
IV
Identification of private reactions. Solving problems in the process of teaching chemistry.
V
Control task: the course of the analysis of cations of the II analytical group - the formation of research skills.
VI
Decoration of private reactions and mixture analysis results of the II analytical group according to the given
schemes.
VII
Evaluation system for laboratory work
VIII
Synthesis of information - multi-component analysis of the study material.
Stage I: General Characterization of II Analytical Group Cations
Analytical classification of ions differs from d.i. The distribution of chemical elements in groups in Mendeleev's
periodic system is based on certain regularities related to the solubility of some compounds, the acid-base
properties of oxides and hydroxides of elements, the dependence of metal cations on hydrochloric acid, sulfuric
acid, and alkalis and is represented by 6 analytical groups of cations and 3 anions.
and
belong to II analytical group of cations with acid-base system. Silver and mercuric
chlorides are insoluble in water. Lead chloride, however, dissolves slightly in cold water and more readily in hot
water.
and
are colorless in aqueous solutions. In addition to chlorides, iodides, bromides,
sulfides, carbonates, phosphates, chromates and oxalates are insoluble in water from their salts, sulfates are
slightly soluble. Discussion of this issue helps students to remove, separate and identify sediments of different
composition using a systematic method in the process of performing the control task.
Silver has an
electron on the outer valence layer, after giving it up it turns into a single charge cation, its
properties are very different from the properties of cations of analytical group I, which is explained by the
formation of the
electronic configuration. The
cation has a charge two units lower than the group
number. This is explained by the effective detection of the inert pair
, which is expressed by the resistance
of the
electron pair on the outer layer to participate in the formation of a covalent bond. Mercury is hardly
oxidized to
ion, since it contains a
electron pair, which is weakly screened by the sublevel and
because of this is strongly bound by the charge of the nucleus. Cations of analytical group II with hardly
polarizable anions
and others form water-soluble salts. (Evaluation indicators - the student
should be able to: [Characterization of the properties of elements, including metals/non-metals and their
important compounds based on the location of elements in the periodic system (Chemistry, Natural Sciences
1,4,6,7,8,9,11,12,13), (Chemistry, Natural Sciences 2 ,6,7,8, 9,11)] explanation of the properties of substances
based on the electronic structure of the atom.
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A group reagent is dilute hydrochloric acid, which reacts with group II cations to form hard-to-dissolve chlorides.
When heated, the solubility of lead chloride in water increases, while the solubility of silver and mercury
chlorides does not change. This property allows the
cation to remove
and
. The analytical
method of removing cations is also used to remove
and
cations. Mercury (I) chloride reacts with
ammonia solution to form dimercurammonium chloride. It is unstable and breaks down. The following diagram
clearly shows the current processes:
Reaction Scheme:
Ag⁺ + HCl → AgCl (White precipitate, turns black in light, soluble in ammonia)
[Hg₂]²⁺ + HCl → Hg₂Cl₂ (White precipitate, turns black in light)
Pb²⁺ + HCl → PbCl₂ (White precipitate, dissolves in hot water, concentrated alkalis)
↓
[Hg₂NH₂]Cl → [HgNH₂]Cl + Hg
When using concentrated hydrochloric acid, soluble complex acids are formed:
AgCl + 2HCl = H₂[AgCl₃]
PbCl₂ + 2HCl = H[PbCl₃]
The information in the tables reduces the time needed to create different types of presentations.
Stage II: Chemical Bases of Toxic Effect of Heavy Metals - Integration with Ecology
Integration motivates students to study chemistry and helps them become competitive individuals. Students learn
that heavy metals have a molecular weight above 50 and a density exceeding 5 g/cm³. In small amounts, they
are essential for organisms, but excessive levels can lead to poisoning. Heavy metals in animal and human body:
• damages the central nervous system;
• changes blood composition;
• negatively affects the functions of the cardiovascular system, liver, lungs, kidneys and other organs;
• can cause acute physiological changes, malignant tumor, allergy, dystrophy, physical and neurological
degenerative processes, which are characterized by symptoms similar to Alzheimer's and Parkinson's
diseases.
According to Knorte's (1974) stress index, heavy metals rank third among pollutants as toxic substances. 3
main ways of their spread were identified: 1. abiotic (wind erosion, water circulation), 2. biotic; 3.
anthropogenic. From the second analytical group of cations, lead and mercury are particularly highly toxic. [2]
Table #2: Historical Heavy Metal Toxicity Events and Modern Regulations
Heavy
Metal
Historical Event /
Period
Health Effects
Observed
Current WHO/FAO
Standards
Modern Sources of
Exposure
Lead (Pb)
Roman Empire (c. 146
BC – 476 AD): Lead
content in bones 100×
higher than modern
humans; widespread use
of lead pipes and vessels
• Neurological
disorders
• Developmental
delays
• Osteoporosis
• Collapse of
• Water: 0.03 mg/L
• Air: 0.0003 mg/m³
• Daily intake: 0.2–
0.3 mg (food), 0.02
mg (water)
• LD₁₀₀: < 5 mg/kg
• Tetraethyl lead in fuel
• Industrial dust and
vapors
• Lead-glazed ceramics
• Packaging materials
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Roman society
(hypothesized)
• Cigarette smoke (13
μg per cigarette)
Lead (Pb)
Greenland Ice Core
Analysis: Elevated lead
levels during Roman
period confirmed in ice
samples
• Historical
atmospheric
pollution
• Long-range
environmental
impact
Same as above
• Fuel combustion
byproducts
• Mining and smelting
• Battery manufacturing
Mercury
(Hg)
Industrial Revolution
(18th–19th centuries):
Mercury used in felt
production; Hatters’
disease documented
• Severe
neurological
disorders
• “Mad Hatter”
syndrome
• Tremors and
psychosis
• Water: 0.0005 mg/L
• Air: 0.0005 mg/m³
• LD₁₀₀: < 5 mg/kg
• Combustion
emissions
• Electrical industry
• Pulp and paper
production
• Caustic soda
manufacturing
• Mercury-based
fungicides
Mercury
(Hg)
Minamata Disease,
Japan (1956): Industrial
mercury discharge into
coastal waters
• Severe
neurological
damage
• Birth defects
• Paralysis and
death
Same as above
• Volcanic activity
(natural)
• Mercury-rich
geological formations
• Coal combustion
• Improper disposal of
medical waste
Table #3: Current Environmental and Safety Standards for Group II Heavy Metals
Heavy
Metal
WHO
Drinking
Water
Limit
Air
Quality
Limit
Daily
Food
Intake
(FAO)
Toxicity
Classification
Primary Health
Impacts
Key
Biochemical
Mechanism
Lead
(Pb)
0.03 mg/l
(30 ppb)
0.0003
mg/m³
0.2-0.3
mg/day
(adult)
LD₁₀₀ < 5
mg/kg (highly
toxic)
Heart pain<br>-
Hemoglobin
synthesis
decrease<br>-
Malignant
tumors<br>- Birth
defects<br>-
Osteoporosis
Bone deposition
(serious
depositor)<br>-
Vitamin D
metabolism
disruption<br>-
Cell energy
balance
disturbance<br>-
Genetic
apparatus
damage
Mercury
(Hg)
0.0005
mg/l (0.5
ppb)
0.0005
mg/m³
Not
established
(minimize
exposure)
LD₁₀₀ < 5
mg/kg (highly
toxic)
Severe
neurological
disorders<br>-
Brain damage<br>-
Immune system
suppression<br>-
Interaction with -
SH protein
groups:<br>2R-
SH + Me²⁺ → R-
S-Me-S-R +
2H⁺<br>-
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Metabolic
disruption
Enzyme
inactivation<br>-
Protein structure
alteration
Silver
(Ag)
0.1 mg/l
(100 ppb)
Not
established
Trace
amounts
(0.02
mg/kg
body
weight)
Low toxicity
(used
medicinally)
Oligodynamic
effect
(antibacterial)<br>-
Generally safe at
low concentrations
Bacterial
inhibition<br>-
Sterile zone
formation<br>-
Antimicrobial
action
Detailed Toxicological Profiles
Lead, Plumbum is one of the most common and dangerous toxicants. The facts of human poisoning with
this element c. BC was described by Greek doctors. According to historians, lead pottery played a crucial role
in the collapse of the Roman Empire. The lead content in the bones of the Romans was 100 times higher than
that of modern people. The Romans used lead to make water pipes and vessels. Analyzing ice from Greenland
icebergs has shown high lead concentrations in the human body during the Roman Empire.
Currently, this element is intensively polluting the biosphere. According to FAO data, an adult person receives
0.2-0.3 mg of lead daily with food and 0.02 mg with water - a biotic way of contamination with heavy metals.
Anthropogenic sources of pollution are: dusty, vaporous, liquid wastes of the enterprise, fuel combustion
products, transport emissions (to increase the detonation number,
is added to tetraethyl lead). [9]
Contamination of food products with lead occurs from packaging material, lead-glazed ceramic dishes. Bone is
a serious depositor. High concentration of causes osteoporosis, decalcification of bones, disturbance of D-
vitamin metabolism, changes in cell energy balance and genetic apparatus. In case of chronic poisoning, pertonia
develops, which is caused by damage to the kidneys. Experimental data have confirmed that when 1 mg of
dust is absorbed, pains in the heart area, decrease in hemoglobin synthesis, development of malignant tumors,
pathologies in the offspring are observed. 1 stick of cigarette contains 13 μg of , 1.5 μg gets into the tobacco
smoke and 1/3 goes into the blood. According to the International Health Organization (WHO), the maximum
permissible concentration of in drinking water is
part per billion or 0.03 mg/l,
in air - 0.0003 mg/m³. [6] The dose of toxic compounds is determined by LD
and LD
(Lethal Dose) - a
dose that causes the death of 50% or 100% of experimental or test animals when taken orally once. The dose is
determined by concentration. All substances with a low LD are toxic. Lead and mercury are especially toxic,
since LD
< 5 mg/kg. Even in the distant future, the amount of maximum permissible concentration equal to
(and even less than) the modern demand should not cause any disease, pathological or genetic change in the
body.
Mercury, (hydrargyrum, Hg) and its compounds are the most volatile of heavy metals, which is the main reason
for its spread and is especially dangerous for living organisms. When inhaled, it passes from the lungs into the
blood, enters the brain, which causes severe neurological disorders. The neurotoxic effect is caused by its
interaction with the group of proteins:
. As a result of
their blocking, the properties of protein substances of tissues change and the properties of hydrolytic, redox
enzymes are inactivated, the immune system decreases. Mercury negatively affects the metabolism of nutrients,
vitamin , calcium, copper, zinc, protein substances.
Industrial mercury polluters include heating combustion, electrical and pulp industries, caustic soda production,
and the use of mercury-containing fungicides. Among the natural sources, volcanic eruptions, mountain rocks,
and mercury deposits are noteworthy.
Solutions of mercury (I) salts contain the group and during dissociation they give us a complex
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cation
All mercury salts are toxic. According to WHO, the maximum permissible concentration of Hg
in drinking water is 1 ppb or 0.0005 mg/l, in air - 0.0005 mg/m³.
Integration with Human Life Safety
We can highlight several issues in the process of teaching chemistry and human life safety: the main risks and
dangers of chemical laboratories, first aid for severe poisoning, thermal and severe burns, the nature and degree
of harmful effects of toxic compounds on human health.
Stage III: Importance and Use of Metal Cations in Medicine - Integration with Medicine
Silver does not belong to a biogenic element, but it is necessary for the normal functioning of a number of organs
of living beings. A small concentration of silver ions increases the body's ability to fight against infectious
diseases, since bacteria do not multiply around it, a sterile zone is formed. It is characterized by oligodynamic
(Greek Oligos – small, Dinamus – strength) action. Traces of ultratrace element silver (0.02 mg/kg) are found
in all living organisms. The highest content of silver in the human body is in the brain (0.03 mg).
Medical Preparations of Metal Cations of Analysis Group II [10]
Silver (Ag⁺) Compounds:
• Silver solutions are used to stabilize drugs, especially to extend the shelf life of eye drops;
• Silver nitrate, Argenti nitras - a pharmacopoeial drug, with antiseptic, bactericidal properties, is used
in the form of a 1-2% aqueous solution for the treatment of eye and skin diseases, during inflammation
of the mucous membrane, in urology, as a burning agent - in dermatology, to treat wounds in surgery; A
weak solution of silver and ammonia complex used in medicine called Amargen works more effectively.
• Protargol (8%) and Cholargol (70%) are highly dispersed powders of colloidal metallic silver, each
crystal (1 μm) is surrounded by a protein shell of albumin (Protargol) or collagen (Colargol). It is used
to rinse the urethra, in conjunctivitis, chronic gastritis, stomach ulcer disease, in dermatology;
• Colloidal nanosilver is a natural antibiotic, antimycotic, antiviral, anthelmintic remedy.
• Electrolytic silver is used in hygiene to deodorize drinking water, mineral water, food products, in
medical and preventive practice.
Lead (Pb²⁺) Compounds:
•
are used in medical practice. They have astringent, antiseptic action.
• During X-ray therapy, diagnosis, a 2-3 mm layer of lead is enough to protect people from X-ray radiation.
The apron, helmet, gloves of the medical personnel of the X-ray rooms are made of rubber containing
lead.
Mercury (Hg) Compounds:
•
is an astringent, burning and antiseptic agent for ulcers (dilution 1:1000), for disinfection;
•
for the treatment of syphilis;
•
as an ointment, in dermatology;
•
calomel, as a business, bilious, diuretic agent.
The student sees the purpose of the task, the practical aspects of these ions, compounds of elements, the need for
human health and the connection with everyday life.
Stage III-B: Case Studies and Active Learning Exercises
This stage introduces real-world scenarios to strengthen students' critical thinking, problem-solving skills, and
appreciation of chemistry's societal relevance. Through active learning exercises, students apply theoretical
knowledge to practical situations involving heavy metal contamination, occupational safety, and environmental
management.
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Case Study 1: Lead Contamination in Drinking Water
Scenario
A small community of 5,000 residents discovers elevated lead levels in its drinking water (0.08 mg/L), nearly
triple the WHO limit (0.03 mg/L). The source is traced to aging lead pipes installed 80 years ago. Children
exhibit symptoms of lead exposure, including learning difficulties and behavioral changes.
Student Tasks (Condensed):
• Calculate daily lead intake from water and compare it to FAO guidelines.
• Assess health risks and identify vulnerable groups.
• Propose three practical remediation strategies and a monitoring plan.
• Draw historical parallels with lead use in the Roman Empire and modern cases (e.g., Flint, Michigan).
Learning Outcome:
Students develop skills in toxicological risk assessment, historical comparison, and public health
communication.
Case Study 2: Mercury Exposure in Industrial Settings
Scenario:
A 42-year-old employee at a chemical plant using mercury cell technology presents with tremors and memory
loss. Air monitoring reveals mercury vapor levels of 0.0012 mg/m³, exceeding WHO limits. Blood tests confirm
elevated mercury levels.
Student Tasks (Condensed):
• Calculate daily and cumulative mercury exposure.
• Explain Hg²⁺ interaction with protein –SH groups and its neurological effects.
• Recommend protective equipment, engineering controls, and biological monitoring.
• Assess environmental risks and compare natural vs. anthropogenic mercury sources.
Laboratory Component:
Students simulate mercury detection using potassium iodide, observing the characteristic Hg₂I₂ precipitate.
Learning Outcome:
Students apply biochemical principles to occupational toxicology, design safety protocols, and evaluate ethical
responsibilities in industrial health.
Active Learning Module: Pollution Management Simulation
Students work in small groups as environmental consultants addressing heavy metal contamination in a mixed-
use area. The scenario involves elevated levels of lead (Pb) and mercury (Hg) in soil, water, and air near a former
battery recycling site, affecting 1,200 residents and local agriculture.
Tasks include:
• Prioritizing risks using WHO/FAO standards
• Designing short- and long-term remediation strategies
• Selecting appropriate analytical methods
• Developing a public communication plan
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Learning Outcome:
Students integrate toxicological data, environmental policy, and analytical chemistry to solve complex, real-
world contamination challenges collaboratively.
Stage IV: Private Reactions for Identification of Group II Cations
After getting acquainted with the theoretical basis of the work, practical aspects are discussed. The analytical
methods used during the test shall be:
• specific;
• sensitive;
• in relation to the precise norms defined by the article of the pharmacopoeia (in the case of medicinal
products) or other normative-technical document;
• short execution time;
• requires a minimum number of research objects.
Systematization of a large volume of information in the form of a table contributes to its better perception, long-
term memorization, material processing, deepening and activation of given knowledge. The student is introduced
to the specific work, its theoretical and methodological material, the purpose and principle of the experiment,
the course of the experiment and the procedure for drawing up the protocol. Procedural knowledge is organized
by activities, helps to build research skills and enables the application of theoretical knowledge with practical
aspects. This method serves to acquire this type of knowledge.
Table #4: Particular Identification Reactions
Cation
Reaction number, reagent
The product of the reaction and its properties
1.
black precipitate, dissolves in ammonia.
brick-red precipitate.
pale yellow precipitate.
yellow precipitate.
1.
2.
sulfates
3.
4.
iodide ion
5. Diphenyldithiocar-
basone (dithizone)
6.
Sulphide ion
white precipitate; Dissolves in acids, alkalis.
white precipitate; Soluble in alkalis and ammonium acetate.
yellow precipitate.
yellow precipitate. Dissolves in excess
- iodide ion.
brick-red precipitate.
C
6
H
5
-
NH - N
C
6
H
5
-
N= N
C = S
S = C
Pb
N - NH - C
6
H
5
N = N - C
6
H
5
kompl eqsi (wi Tel i )
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A black precipitate dissolves in nitric acid.
1.
2.
3.
Diphenylcarbazide
O = C
NH - NH - C
6
H
5
N = N - C
6
H
5
Black precipitate.
Red precipitate.
Black precipitate.
Black precipitate. Amalgam on copper.
Violet or blue precipitate.
A dark green precipitate dissolves in excess iodide
[
]
Stage V: the control task is carried out in groups (maximum 3-4 students). Group (collaborative) work –
teaching with this method involves dividing students into groups and giving them an experimental task. Work is
distributed in advance. Each student is in the role of a detective and tries to discover the cation or cations
contained in a solution of unknown composition using the given system analysis method, with the help of a
scheme, independently writes and organizes the results of the experiment in a workbook, interprets his own
observations and draws conclusions as a result of judgment, thus instilling in him the desire to constantly strive
to satisfy curiosity, which is a necessary prerequisite for the formation of enthusiasm for scientific research work.
Thus, work is carried out in groups, but decoration is done individually. This strategy ensures maximum
involvement of all students in the learning process. Through the control task, students' theoretical knowledge is
checked and it helps to develop critical thinking. They are given the opportunity to become researchers
themselves, and this process is facilitated by the teaching material provided with methodically organized tables
and diagrams that show the way how they arrived at this discovery.
It is represented by the acid-base classification of group II
Current analysis scheme of cations by systematic method
The purpose of the work: detection of group II cations in the research solution.
Assignment: students should determine group II cations in the research solution, and for this purpose they use
the method of systematic analysis.
The course of the experiment: 20-30 drops of the test solution are placed in a conical flask, and 2N hydrochloric
acid solution is added. The experiment separates and centrifuges the precipitate. The precipitate is processed 2-
3 times with hot water and centrifuged again. Lead (II) chloride dissolves in the solution, while silver chloride
and mercury (I) chloride form a precipitate.
1. Discovery of
cation. 3-5 drops of the centrifuge are added to the potassium iodide solution. A yellow
precipitate of lead iodide
is formed, which dissolves when heated, and is separated again as a golden
needle-like precipitate when cooled.
C
6
H
5
-
NH - N
C
6
H
5
-
N = N
C = O
O = C
N - NH - C
6
H
5
N = N - C
6
H
5
Hg
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2. Discovery of
cation. Ammonium alkali is added to the precipitate and mixed. In the presence of
cation, the precipitate turns black. Under the action of
, silver chloride passes into the
solution in the form of a complex salt, while
salt and mercury remain in the precipitate. The
precipitate is centrifuged.
3. Discovery of
cation. The centrifuge is divided into two parts. Potassium iodide solution is added to
one of them, nitric acid to the other. In the presence of
cation, a yellow precipitate of silver iodide will
precipitate in the first test tube, and a white precipitate of silver chloride will precipitate in the second. [5]
Scheme of analysis of group II cations
The experiment is carried out with appropriate comments. If it is difficult for the student to make a conclusion,
the teacher should lead him to the correct formulation with the help of questions and tests. Only in this case the
work is considered completed.
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VI stage: drawing up the results of private reactions and mixture analysis of the II analytical group according to
the given schemes.
The results of private reactions and mixture analysis of the II analytical group are drawn up according to the
given tables in the workbooks, which are filled in according to the results of the performed experiment:
Private reactions of cations ІI analytical group
Table # 3
1
2
3
4
5
6
Number
Reagent
Cation reaction
equation
Reaction
equation
Conditions for
the reaction
Characterization of
the product obtained
Analysis of a mixture of cations of the analytical group
Table# 4
1
2
3
4
5
6
7
Sample
number
Research
ion
Reagent
What did
we see?
Conclusion
Sediment
composition
Solution
composition
Stage VII: Weekly laboratory work is evaluated with 1 point. The goal of the weekly laboratory evaluation is
to ensure students are progressing in their understanding of analytical group II cations and can effectively apply
theoretical knowledge to practical experiments. It determines the research procedures, collects data, analyzes
them, draws conclusions based on reasoned reasoning, adheres to ethics and safety norms while conducting
research work. [11] The evaluation process is designed to be transparent, with students receiving feedback on
their performance in each criterion weekly. This helps them track their progress and improve in specific areas.
Evaluation of laboratory work 0
Table # 5
Evaluation criteria
points
comment
1.
Doing homework - tests, tasks
0-1
Criteria: Completeness and accuracy of assigned
homework and preparatory tasks.
0 points: Homework incomplete or inaccurate.
1 point: Homework completed fully and accurately.
2.
General characterization of the
cations of the II analytical
group, consideration of the
theoretical part of private
reactions with the teacher
0-5
Criteria: Participation in discussions, ability to explain
theoretical aspects, and characterization of cations.
0-2 points: Limited understanding or incorrect
explanations.
3-4 points: Moderate understanding with minor
inaccuracies.
5 points: Comprehensive and accurate understanding.
INTERNATIONAL JOURNAL OF RESEARCH AND INNOVATION IN APPLIED SCIENCE (IJRIAS)
ISSN No. 2454-6194 | DOI: 10.51584/IJRIAS |Volume X Issue X October 2025
www.rsisinternational.org
Page 1140
3.
Planning of the experiment,
detailed description of its
progress, conducting
identification reactions under
the guidance of a laboratory
assistant, a teacher
0-2
Criteria: Organization of experimental steps, adherence to
safety norms, and proper execution.
0 points: Poor planning or failure to execute safely.
1 point: Partial planning and execution.
2 points: Well-planned and safely executed experiment.
4.
Filling in the workbook in the
form of tables, diagrams,
confirmation by the signature
of the laboratory assistant
0-1
Criteria: Accuracy and neatness of recorded results in
tables/diagrams.
0 points: Workbook incomplete or disorganized.
1 point: Workbook complete and well-organized.
5.
Presentation of work, use of
information and
communication technologies
0-1
Criteria: Effectiveness in presenting results using ICT tools
(e.g., slides or diagrams).
0 points: Lack of ICT usage or ineffective presentation.
1 point: Clear and well-supported presentation with
appropriate tools.
6.
final evaluation
1
This point is awarded based on the overall performance and
adherence to safety and ethical norms.
Students will receive both verbal and written feedback from the instructor and laboratory assistant. Feedback
will focus on strengths, areas for improvement, and recommendations for the next session. Weekly points are
cumulative and contribute significantly to the final laboratory grade. Consistent performance across all
evaluation criteria is essential for achieving a high overall score.
Stage VIII: synthesis of information - multi-component analysis of the study material
The study of Analytical Group II cations provides students with a structured framework to understand the
fundamental principles of chemical analysis and their real-world applications. Through the combination of
theoretical instruction, practical experiments, and interdisciplinary integration, this methodology fosters a deep
understanding of the chemical properties and behavior of cations in various contexts.
The implementation of the base-acid classification system as the primary analytical method enhances students'
logical and critical thinking skills. This system not only simplifies the identification and separation of cations
but also promotes environmentally safer practices compared to traditional methods like the sulfide analysis. By
emphasizing principles such as solubility, amphotericity, and complex formation, students gain a clear
understanding of the chemical behavior of metals like silver, mercury, and lead, which are crucial for advanced
studies and research.
The integration with ecology, medicine, and human life safety underscores the relevance of chemistry in
addressing societal challenges. For example, the toxicological study of heavy metals like lead and mercury
demonstrates the environmental and health implications of chemical substances. Similarly, the applications of
silver compounds in medicine illustrate the importance of analytical chemistry in developing effective treatments
and improving human health.
The hands-on approach through laboratory experiments enables students to connect theoretical knowledge with
practical execution. The systematic analysis of cations, the use of group reagents, and the identification of
reaction products are key skills that prepare students for careers in science and technology. Moreover, the
INTERNATIONAL JOURNAL OF RESEARCH AND INNOVATION IN APPLIED SCIENCE (IJRIAS)
ISSN No. 2454-6194 | DOI: 10.51584/IJRIAS |Volume X Issue X October 2025
www.rsisinternational.org
Page 1141
structured evaluation system ensures that students develop research skills, adhere to safety and ethical standards,
and refine their experimental techniques.
By synthesizing information across disciplines, students are encouraged to think critically and holistically about
the chemical processes around them. The emphasis on creative teaching methods, such as collaborative group
work, detailed feedback, and the use of ICT tools, equips them with the skills needed to tackle complex problems
and excel in professional environments.
In conclusion, the study methodology of Analytical Group II cations provides a comprehensive educational
experience that integrates theory, practice, and interdisciplinary applications. By mastering these concepts,
students are empowered to understand and address chemical, environmental, and societal issues, laying a strong
foundation for their future endeavors in science and beyond.
Integration of Theoretical and Practical Knowledge
The implementation of the base-acid classification system as the primary analytical method enhances students'
logical and critical thinking skills. This system not only simplifies the identification and separation of cations
but also promotes environmentally safer practices compared to traditional methods like sulfide analysis. By
emphasizing principles such as solubility, amphotericity, and complex formation, students gain a clear
understanding of the chemical behavior of metals like silver, mercury, and lead, which are crucial for advanced
studies and research.
The systematic approach presented in this methodology follows a clear pedagogical progression:
Foundation (Stage I): Students begin with fundamental chemical principles, electronic configurations, and
group reagent behavior, establishing the theoretical framework necessary for all subsequent work.
1. Contextualization (Stages II-III): The integration with ecology, medicine, and human life safety
underscores the relevance of chemistry in addressing societal challenges. For example, the toxicological
study of heavy metals like lead and mercury demonstrates the environmental and health implications of
chemical substances. The historical examples presented in Table #2 provide students with compelling
evidence of chemistry's long-term impact on human civilization, from the Roman Empire's lead poisoning
to modern environmental regulations. Similarly, the applications of silver compounds in medicine (Stage III)
illustrate the importance of analytical chemistry in developing effective treatments and improving human
health.
2. Active Application (Stage III-B): The newly introduced case studies bridge the gap between theoretical
knowledge and practical problem-solving. Students engage in realistic scenarios involving lead
contamination in water supplies, occupational mercury exposure, and silver-based purification systems.
These exercises develop critical thinking skills, quantitative assessment abilities, and appreciation for the
complexity of real-world environmental and health challenges. By grappling with scenarios that have no
single "correct" answer, students learn to evaluate trade-offs, consider multiple stakeholder perspectives, and
make evidence-based recommendations.
3. Technical Mastery (Stages IV-V): The hands-on approach through laboratory experiments enables students
to connect theoretical knowledge with practical execution. The systematic analysis of cations, the use of
group reagents, and the identification of reaction products are key skills that prepare students for careers in
science and technology. The introduction of modern instrumental techniques (AAS, ICP-MS) alongside
classical methods ensures students understand both the historical foundations and contemporary practice of
analytical chemistry. The extended control tasks push beyond simple identification to include quantitative
estimation, regulatory compliance assessment, and environmental risk evaluation.
4. Documentation and Assessment (Stages VI-VII): The structured evaluation system ensures that students
develop research skills, adhere to safety and ethical standards, and refine their experimental techniques.
Progressive evaluation throughout the semester encourages continuous improvement while maintaining high
INTERNATIONAL JOURNAL OF RESEARCH AND INNOVATION IN APPLIED SCIENCE (IJRIAS)
ISSN No. 2454-6194 | DOI: 10.51584/IJRIAS |Volume X Issue X October 2025
www.rsisinternational.org
Page 1142
standards. The detailed documentation requirements teach professional scientific communication skills
essential for careers in chemistry, environmental science, and public health.
Interdisciplinary Connections and Societal Relevance
One of the strongest features of this methodology is its emphasis on interdisciplinary integration:
Chemistry ↔ Ecology: Students learn how chemical principles govern environmental contamination,
bioaccumulation, and ecosystem health. The three pathways of heavy metal spread (abiotic, biotic,
anthropogenic) from Knorte's stress index provide a framework for understanding human impact on natural
systems. The comparison of historical and modern contamination levels (Table #2 and #3) demonstrates both
the progress made through environmental regulation and the ongoing challenges of industrial society.
Chemistry ↔ Medicine: The medical applications of Group II cations (Stage III) show students that analytical
chemistry is not merely academic but directly improves human health. From silver's oligodynamic antibacterial
action to lead shielding in X-ray rooms, students see how chemical knowledge translates to practical medical
applications. Understanding both the therapeutic uses and toxicological dangers of these elements develops
nuanced thinking about risk-benefit analysis in healthcare.
Chemistry ↔ History: The archaeological and historical examples (Roman Empire lead poisoning, Greenland
ice cores, industrial revolution mercury exposure) demonstrate that chemistry provides tools for understanding
human history. Students learn that chemical analysis can answer historical questions and that historical patterns
inform modern safety standards. This connection makes chemistry feel relevant beyond the laboratory.
Chemistry ↔ Public Policy: The WHO and FAO regulatory standards presented throughout the document
show students how scientific evidence informs public health policy. The case studies requiring students to make
recommendations for contaminated communities or industrial safety improvements prepare them for potential
roles in environmental regulation, occupational health, or policy advocacy.
Development of Critical Competencies
This methodology systematically develops multiple competencies essential for modern scientific practice, such
as analytical skills, critical thinking, problem-solving, communication, ethical awareness, traditional approaches,
among others. The study methodology of Analytical Group II cations presented in this article provides a
comprehensive educational experience that integrates theory, practice, and interdisciplinary applications. By
synthesizing information across disciplines, students are encouraged to think critically and holistically about the
chemical processes around them. The emphasis on creative teaching methods, such as collaborative group work,
detailed feedback, and the use of ICT tools, equips them with the skills needed to tackle complex problems and
excel in professional environments.
The historical context provided through examples like Roman lead poisoning and Greenland ice core analysis
helps students understand that chemistry is not a static body of knowledge but an evolving science that has
shaped and continues to shape human civilization. Toxicological information and regulatory standards teach
students that chemical knowledge carries ethical responsibilities and that analytical chemists play crucial roles
in protecting public health and environmental quality.
The case studies and active learning exercises introduced in Stage III-B transform abstract chemical concepts
into concrete problem-solving scenarios. Students learn that identifying a yellow lead iodide precipitate is not
merely an academic exercise but a skill that could help diagnose environmental contamination threatening a
community's health. They understand that recognizing mercury's interaction with protein -SH groups explain
real neurological symptoms in occupationally exposed workers. They appreciate that silver's oligodynamic effect
represents a practical alternative to chemical disinfectants in healthcare settings.
The integration of classical wet chemistry methods with modern instrumental techniques prepares students for
the realities of contemporary analytical practice. They learn that while AAS and ICP-MS offer superior
INTERNATIONAL JOURNAL OF RESEARCH AND INNOVATION IN APPLIED SCIENCE (IJRIAS)
ISSN No. 2454-6194 | DOI: 10.51584/IJRIAS |Volume X Issue X October 2025
www.rsisinternational.org
Page 1143
sensitivity and speed, the fundamental understanding gained through hands-on qualitative analysis remains
essential for method development, troubleshooting, and interpreting instrumental results. This balanced
perspective ensures graduates are not merely technicians who can operate equipment but knowledgeable
scientists who understand the chemistry underlying their measurements.
The progressive evaluation system, with its emphasis on continuous improvement and multi-faceted assessment,
develops not only technical competence but also communication skills, collaborative abilities, and professional
habits. Students learn that scientific work requires not just correct results but also clear documentation, effective
presentation, and ethical conduct. The weekly feedback mechanism ensures students receive guidance for
improvement rather than simply receiving scores.
By mastering these concepts and skills, students are empowered to understand and address chemical,
environmental, and societal issues. They leave the course not only able to identify Group II cations but also
capable of: assessing environmental contamination risks, evaluating occupational safety protocols, interpreting
regulatory standards, communicating technical information effectively, integrating knowledge across
disciplinary boundaries, thinking critically about complex real-world problems.
This methodology thus lays a strong foundation for students' future endeavors in science and beyond, whether
they pursue careers in analytical chemistry, environmental science, public health, education, or related fields.
More importantly, it cultivates scientifically literate citizens who understand the role of chemistry in society and
can contribute to informed decision-making about environmental and health issues affecting their communities
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