Tin and Transition Metals for SS 3

Class: SS 3
Term: First Term
Week: 3
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Metals and Their Compounds
Previous Lesson: Alkaline Earth Metals and Their General Properties
Topic: METALS AND THEIR COMPOUNDS
Subject Matter: Tin: extraction of tin and uses of tin; Transition metal: properties of transition metals; (the first transition series only)

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• Describe the extraction process of tin from its ore.
• State at least three uses of tin.
• List the elements of the first transition series.
• Explain the electronic configuration of the first transition series elements.
• Identify at least three general properties of transition metals.
• Discuss the variable oxidation states of transition metals with examples.
• Explain the formation of complex compounds by transition metals.

Affective Domain

• Appreciate the industrial importance of tin and transition metals.
• Show interest in learning more about the chemistry of metals.

Psychomotor Domain

• Draw a simple diagram illustrating the extraction of tin.
• Identify transition metals on a periodic table.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Essential Chemistry for Senior Secondary Schools by O. Y. Ababio
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• A chart showing the periodic table highlighting transition metals.
• Diagrams illustrating the extraction of tin.
• Samples of tin metal or products containing tin (e.g., solder, tin cans).
• Chart displaying the electronic configurations of the first transition series.
• Chart showing examples of coloured transition metal compounds.

Rationale for the Lesson

This lesson is important as it introduces students to the industrial significance of tin and the unique chemical characteristics of transition metals. Understanding these concepts provides a foundation for further studies in inorganic chemistry and their applications in various industries, from manufacturing to catalysis.

Prerequisite/Previous Knowledge

Students should have prior knowledge of the periodic table, basic concepts of metals and non-metals, and electronic configuration of elements.

Lesson Content/Board Summary

METALS AND THEIR COMPOUNDS

Tin

Extraction of Tin

Tin is primarily extracted from its main ore, cassiterite ((SnO_2)), which is tin(IV) oxide. The extraction process involves several steps:

1. Crushing and Washing: The ore is first crushed into a fine powder and then washed to remove lighter impurities like sand and clay. This process is called gravity separation due to the high density of cassiterite.
2. Roasting: The concentrated ore is roasted in air to remove impurities such as sulphur (as (SO_2)) and arsenic (as (As_2O_3)). Any iron present is converted to iron(III) oxide.
3. Magnetic Separation: After roasting, the mixture is subjected to magnetic separation to remove magnetic impurities like iron(III) oxide.
4. Reduction: The purified cassiterite is then mixed with powdered charcoal (carbon) and heated strongly in a reverberatory furnace at about (1200^circ C). Carbon reduces the tin(IV) oxide to molten tin metal.

(SnO_2(s) + 2C(s) rightarrow Sn(l) + 2CO(g))

5. Refining: The molten tin is further refined by heating it gently on a sloping hearth, allowing the pure tin to flow away from higher melting point impurities. Electrolytic refining can also be used for higher purity.

Uses of Tin

Tin is a versatile metal with various applications, including:

1. Tin Plating: Used to coat steel sheets (tin plates) to prevent corrosion, especially for food cans, as tin is non-toxic and resistant to corrosion.
2. Alloys: It is an important component in several alloys:
   • Solder: An alloy of tin and lead, used for joining metals in electronics.
   • Bronze: An alloy of copper and tin, used for statues, bells, and coins.
   • Pewter: An alloy of tin, copper, antimony, and bismuth, used for decorative items and tableware.
3. Chemical Compounds: Tin compounds are used in ceramics, glazes, and as catalysts.
4. Float Glass Production: Molten tin is used as a flat surface for cooling molten glass to produce flat, uniform sheets.

Transition Metals (First Transition Series)

Transition metals are elements that have partially filled d-orbitals in their atoms or common ions. The first transition series consists of elements from Scandium (Sc) to Zinc (Zn) in Period 4 of the periodic table.

First Transition Series Elements

The elements in the first transition series are:

1. Scandium (Sc)
2. Titanium (Ti)
3. Vanadium (V)
4. Chromium (Cr)
5. Manganese (Mn)
6. Iron (Fe)
7. Cobalt (Co)
8. Nickel (Ni)
9. Copper (Cu)
10. Zinc (Zn)

General Properties of Transition Metals

Transition metals exhibit several characteristic properties due to their partially filled d-orbitals and similar atomic radii:

1. Electronic Configuration: They generally have the electronic configuration ([Ar] 3d^{1-10} 4s^{1-2}). For example, Iron (Fe) is ([Ar] 3d^6 4s^2). Chromium ((Cr)) and Copper ((Cu)) show exceptions to achieve more stable half-filled or fully-filled d-orbitals (Cr: ([Ar] 3d^5 4s^1), Cu: ([Ar] 3d^{10} 4s^1)).
2. Variable Oxidation States: Transition metals can exhibit multiple oxidation states, especially in their compounds. This is due to the small energy difference between the ( (n-1)d ) and ( ns ) orbitals, allowing electrons from both orbitals to participate in bonding.

   Examples:

   1. Iron (Fe): +2 (e.g., (FeCl_2)), +3 (e.g., (FeCl_3))
   2. Manganese (Mn): +2, +3, +4, +6, +7 (e.g., (MnO_2), (KMnO_4))
   3. Chromium (Cr): +2, +3, +6 (e.g., (CrCl_2), (Cr_2O_3), (K_2Cr_2O_7))
3. Formation of Coloured Compounds: Most transition metal ions and their compounds are coloured in solution or solid state. This is due to d-d electronic transitions, where electrons absorb specific wavelengths of visible light and are promoted to higher energy d-orbitals, reflecting the complementary colour.
4. Complex Formation: Transition metals readily form complex compounds (coordination compounds) by accepting electron pairs from ligands (ions or molecules) into their empty d-orbitals. The metal ion acts as a Lewis acid, and the ligands act as Lewis bases.

   Examples:

   1. ([Fe(CN)_6]^{3-}) (hexacyanoferrate(III) ion)
   2. ([Cu(NH_3)_4]^{2+}) (tetraamminecopper(II) ion)
5. Catalytic Activity: Many transition metals and their compounds act as excellent catalysts in various chemical reactions. This is attributed to their variable oxidation states and ability to form unstable intermediates.

   Examples:

   1. Iron (Fe) in the Haber process ((N_2 + 3H_2 rightleftharpoons 2NH_3))
   2. Vanadium(V) oxide ((V_2O_5)) in the Contact process ((2SO_2 + O_2 rightleftharpoons 2SO_3))
   3. Nickel (Ni) in the hydrogenation of oils.
6. Paramagnetism: Many transition metal ions are paramagnetic, meaning they are weakly attracted to a magnetic field. This property arises from the presence of unpaired electrons in their d-orbitals.

Teaching Methods/Instructional Techniques

Discussion, Explanation, Question and Answer, Demonstration, Guided Practice, Visual Aids.

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Recalling/Engaging

Teacher’s Activity: The teacher greets the students and asks them to recall what they know about metals from previous classes, specifically mentioning some common metals and their uses.

Pupils’ Activity: Students respond by naming metals like iron, copper, aluminium, and stating some uses like electrical wiring, construction, and cooking utensils.

Learning Point: Review of metals

Step 2: Extraction of Tin

Time: 8 minutes

Teaching Skill: Explaining/Illustrating

Teacher’s Activity: The teacher explains the main ore of tin (cassiterite) and describes the steps involved in its extraction, using diagrams to illustrate the processes of crushing, washing, roasting, reduction, and refining.

Pupils’ Activity: Students listen attentively, observe the diagrams, and ask questions for clarification about the extraction steps.

Learning Point: Tin extraction process

Step 3: Uses of Tin

Time: 5 minutes

Teaching Skill: Listing/Discussing

Teacher’s Activity: The teacher discusses the various uses of tin, focusing on tin plating, its role in alloys like solder and bronze, and other industrial applications. The teacher may show samples of tin products.

Pupils’ Activity: Students identify and list the uses of tin, relating them to everyday items and industrial processes.

Learning Point: Everyday uses of tin

Step 4: Introduction to Transition Metals

Time: 5 minutes

Teaching Skill: Introducing/Identifying

Teacher’s Activity: The teacher introduces transition metals, points them out on the periodic table, and lists the elements of the first transition series (Scandium to Zinc).

Pupils’ Activity: Students locate transition metals on their periodic tables and note down the elements of the first transition series.

Learning Point: First transition series

Step 5: Electronic Configuration and Variable Oxidation States

Time: 8 minutes

Teaching Skill: Explaining/Analyzing

Teacher’s Activity: The teacher explains the general electronic configuration of transition metals and how it leads to their characteristic property of variable oxidation states, providing examples for elements like Iron and Manganese.

Pupils’ Activity: Students listen, take notes, and attempt to write electronic configurations and oxidation states for given transition metals.

Learning Point: Variable oxidation states

Step 6: Coloured Compounds and Complex Formation

Time: 5 minutes

Teaching Skill: Explaining/Illustrating

Teacher’s Activity: The teacher explains why transition metals form coloured compounds (d-d transitions) and their ability to form complex ions, giving examples of common complexes. The teacher may show pictures of coloured compounds.

Pupils’ Activity: Students observe the examples and try to understand the concepts of colour formation and complexation.

Learning Point: Coloured compounds, complexes

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Name the chief ore of tin.
2. State two important uses of tin.
3. List three elements of the first transition series.
4. Give two general properties of transition metals.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Understanding tin and transition metals

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on tin extraction, uses, and transition metal properties into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson notes

Step 9: Conclusion

Time: 0 minutes

Teaching Skill: Summarising

Teacher’s Activity: The teacher briefly summarises the key points of the lesson, emphasizing the importance of tin and the unique characteristics of transition metals. The teacher then dismisses the class.

Pupils’ Activity: Students listen to the summary and prepare for the next lesson.

Learning Point: Lesson consolidation

Continuous Assessment/Further Study

Type: Homework

Instruction: Answer the following questions in your notebook:

1. Describe, in your own words, the main steps involved in the extraction of tin from cassiterite.
2. Explain why transition metals exhibit variable oxidation states. Give two examples.
3. Research and list three other industrial applications of transition metals or their compounds not mentioned in class.
4. Draw a simple sketch of the setup for the reduction of tin(IV) oxide in the extraction process.

Lesson Keywords

• Tin – A soft, silvery-white metal, resistant to corrosion.
• Cassiterite – The main ore of tin, chemically tin(IV) oxide ((SnO_2)).
• Transition Metals – Elements in the d-block of the periodic table, characterized by partially filled d-orbitals.
• First Transition Series – Elements from Scandium to Zinc in Period 4.
• Oxidation State – The degree of oxidation of an atom in a chemical compound.
• Complex Compounds – Compounds formed when a central metal ion (often a transition metal) is bonded to several ligands.
• Ligands – Ions or molecules that donate electron pairs to a central metal atom or ion to form a complex.
• Catalyst – A substance that increases the rate of a chemical reaction without being consumed in the process.

Differentiation

For struggling learners, the teacher can provide simplified diagrams of tin extraction and a pre-filled list of the first transition series elements. For advanced learners, the teacher can challenge them to research the specific electronic configurations of the exceptions (Cr and Cu) and explain why they are exceptions, or to investigate the mechanism of catalytic activity for a specific transition metal catalyst.

Suggested Lesson Videos

For further understanding of tin extraction and transition metals, students can search on YouTube for:

• “Extraction of Tin from Cassiterite”
• “Properties of First Transition Series Elements”
• “Variable Oxidation States of Transition Metals”
• “Complex Formation by Transition Metals”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure all instructional materials, especially the periodic table, diagrams of tin extraction, and charts for transition metal properties, are ready. Begin by engaging students with a brief recap of general metal properties to connect with prior knowledge. Proceed systematically through the extraction and uses of tin, using visual aids to make the process clear. When introducing transition metals, clearly identify them on the periodic table and emphasize the first series. Explain their unique properties (electronic configuration, variable oxidation states, coloured compounds, complex formation, catalytic activity, paramagnetism) with relevant examples. Encourage students to ask questions and participate in discussions. During Step 7, use the evaluation questions to check understanding of both tin and transition metal concepts. Guide students to copy the Board Summary notes accurately in Step 8 to ensure they have a clear record for revision. Conclude by reinforcing the main learning points and their real-world relevance.