Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Periodic Table
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Periodic Table
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Subject: Chemistry
Class: Senior Secondary 2
Term: 1st Term
Week: 1
Theme: The Chemical World
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explain the periodiclaw arrange commonelements in to groups(families) and periods distinguishbetween the familiesof elements on the periodic table discuss the changes in the properties of elementsdown the group and across periods discuss the relationship betweenionization energy and electron affinity and the properties of elements down the groups and acrossperiods explain the diagonal relationshipin the properties of elements
The Chemical World shell (n) that is being filled with electrons for the elements in that period. Elements within the same period have their valence electrons in the same principal energy shell, but their number of valence electrons increases from left to right.
Example: Period 3 includes Na, Mg, Al, Si, P, S, Cl, Ar, all of which have valence electrons in the third energy shell.
Groups (Families): There are 18 vertical columns. Historically, these were often numbered I to VIII (main group elements) and B groups (transition elements). The modern IUPAC numbering system uses 1 to
1
8. Elements within the same main group generally have the same number of valence electrons and thus exhibit similar chemical properties. They form families with distinct characteristics.
Group 1: Alkali Metals (1 valence electron)
Group 2: Alkaline Earth Metals (2 valence electrons)
Groups 3-12: Transition Metals Group 13: Boron Family (3 valence electrons)
Group 14: Carbon Family (4 valence electrons)
Group 15: Nitrogen Family (5 valence electrons)
Group 16: Chalcogens (6 valence electrons)
Group 17: Halogens (7 valence electrons)
Group 18: Noble Gases (8 valence electrons, except Helium with 2) 2.
3. Distinction Between Families of Elements Elements are broadly classified into metals, non-metals, and metalloids based on their properties, and further into specific families within groups.
Metals: Characteristics: Lustrous (shiny), malleable (can be hammered into sheets), ductile (can be drawn into wires), good conductors of heat and electricity, tend to lose electrons to form positive ions (cations), generally solids at room temperature (except Mercury).
Location: Found on the left and centre of the periodic table.
Examples relevant to Nigeria: Iron (construction, tools), Copper (electrical wires), Aluminum (roofing, pots), Gold (jewelry, investment), Tin (alloys, plating).
Non-metals: Characteristics: Dull appearance, brittle (break easily), poor conductors of heat and electricity (insulators), tend to gain or share electrons to form negative ions (anions) or covalent compounds. Can be solids, liquids (Bromine), or gases (Oxygen, Nitrogen, Chlorine) at room temperature.
Location: Found on the right side of the periodic table.
Examples relevant to Nigeria: Carbon (soot, coal, graphite), Oxygen (air, combustion), Nitrogen (air, fertilisers), Sulphur (medicines, vulcanization), Phosphorus (matches, fertilisers).
Metalloids (Semi-metals): Characteristics: Exhibit properties intermediate between metals and non-metals. Often shiny like metals but brittle like non-metals. Semi-conductors of electricity, making them vital in electronics.
Location: Along the zigzag line separating metals from non-metals (e.g., Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium).
Examples: Silicon (computer chips, solar panels – increasing relevance in Nigeria for renewable energy).
Transition Metals (Groups 3-12): Characteristics: Typically hard, strong, high melting/boiling points, form coloured compounds, exhibit multiple oxidation states, good catalysts, paramagnetism.
Examples: Iron, Copper, Zinc, Chromium, Nickel. Widely used in Nigerian industries (e.g., steel production, coinage, catalysts in petrochemicals).
Specific Main Group Families: Group 1 (Alkali Metals): Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs), Francium (Fr).
Properties: Very reactive metals, soft, low melting points, highly electropositive, form +1 ions, react vigorously with water to produce hydrogen gas and metal hydroxide.
Uses: Sodium in common salt (NaCl), Potassium in fertilisers.
Group 2 (Alkaline Earth Metals): Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra).
Properties: Reactive metals, harder and higher melting points than alkali metals, form +2 ions, react with water (less vigorously than Group 1).
Uses: Magnesium in alloys, Calcium in cement and bones.
Group 17 (Halogens): Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (At).
Properties: Very reactive non-metals, highly electronegative, form -1 ions, exist as diatomic molecules (F2, Cl2, Br2, I2), corrosive.
Uses: Chlorine for water purification, iodine as an antiseptic and in iodised salt.
Group 18 (Noble Gases / Inert Gases): Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn).
Properties: Extremely unreactive (inert) due to full valence shells, exist as monatomic gases, colourless, odourless. * Uses: Argon in light bulbs (to prevent filament oxidation), Neon in display signs, Helium in balloons and cryogenics. 2.
4. Changes in Properties Down the Group and Across Periods be posed throughout the lesson to check for understanding of definitions, trends, and examples.
Classwork: Short in-class exercises or quick quizzes on identifying groups/periods, stating trends, or matching elements to their families.
Peer-Assessment: Students could exchange answers for short practice questions and provide feedback based on a teacher-provided answer key. 6.
2. Summative Assessment Questions (aligned with Evaluation Guide): Question 1: State the Modern Periodic Law. (Marking Scheme: 2 marks for correct statement, 1 mark for mentioning atomic number as basis.)
Question 2: Group the following common elements into their respective families (groups) and periods: Magnesium (Mg, Z=12) Fluorine (F, Z=9) Argon (Ar, Z=18) Calcium (Ca, Z=20) (Marking Scheme: 1 mark for each correct group, 1 mark for each correct period. Total 8 marks.)
Question 3: State with examples the distinguishing characteristics of the following blocks of elements: a) Metals (2 characteristics, 1 example) b) Non-metals (2 characteristics, 1 example) c) Transition metals (2 characteristics, 1 example) d) Halogens (2 characteristics, 1 example) (Marking Scheme: 1 mark per characteristic, 1 mark per example. Total 12 marks.)
Question 4: Define the following terms: a) Ionization energy b)
Electron affinity (Marking Scheme: 2 marks for each correct and complete definition. Total 4 marks.)
Question 5: Illustrate the changes in the following properties for main group elements: a)
Atomic radius: i) Down Group 1 (e.g., Li to K) ii) Across Period 3 (e.g., Na to Ar) b)
Metallic character: i) Down Group 2 (e.g., Be to Ba) ii) Across Period 2 (e.g., Li to Ne) Provide clear explanations for each trend. (Marking Scheme: 1 mark for stating trend, 2 marks for correct explanation for each of the four parts. Total 12 marks.)
Question 6: Describe the diagonal relationships observed in the properties of elements in the periodic table, giving one specific example of a diagonally related pair and one property they share. (Marking Scheme: 2 marks for clear description of diagonal relationship, 1 mark for correct pair, 2 marks for specific shared property. Total 5 marks.)
7. Real-life Applications / Integration
1. Industrial Applications (e.g., Oil and Gas, Manufacturing): The Periodic Table helps in understanding the properties of elements used in various Nigerian industries. For instance, the selection of catalysts in petrochemical refining (e.g., transition metals like Vanadium or Platinum compounds) relies on their characteristic properties (multiple oxidation states, ability to form complexes). Similarly, knowledge of metallic properties guides the choice of alloys for pipelines (corrosion resistance), engine parts, or even simple tools manufactured locally. Understanding non-metals like sulphur and phosphorus is vital for fertilizer production, which is key to Nigeria's agricultural sector.
2. Water Treatment and Public Health: Chlorine (a halogen, Group 17) is widely used in Nigeria for water purification to kill harmful microorganisms. Its strong oxidizing power, a predictable property from its position in the periodic table (high electronegativity, high electron affinity), makes it effective. This directly impacts public health by providing safe drinking water in urban and rural areas.
3. Local Crafts and Construction: The unique properties of metals like iron (durability, malleability), copper (conductivity, corrosion resistance), and aluminum (lightweight, corrosion resistance) are crucial in various local crafts (e.g., blacksmithing, jewelry making) and in the construction industry (e.g., steel reinforcement, aluminum roofing sheets). Knowledge of these properties, derived from their positions on the Periodic Table, informs their suitability for specific applications. For example, the high reactivity of alkali metals means they are never used structurally, unlike the relatively inert transition metals.
8. Differentiation, Remediation and Extension 8.
1. Differentiation: Group Work: Allow students to work in mixed-ability groups where stronger students can support weaker ones in understanding concepts and completing tasks.
Visual Aids: Provide printed periodic tables with key groups and periods colour-coded for visual learners and those who struggle with abstract concepts.
Varied Questioning: Pose simpler, recall-based questions to struggling learners first, gradually increasing complexity for all students. 8.
2. Remediation (for struggling learners): Simplified Explanations: Re-explain key concepts like periodic law and trends using simpler language and more concrete analogies.
Visual Reinforcement: Provide large, colourful periodic table charts. Use mnemonic devices to remember group names or trends.
Targeted Practice: Assign ones in understanding concepts and completing tasks.
Visual Aids: Provide printed periodic tables with key groups and periods colour-coded for visual learners and those who struggle with abstract concepts.
Varied Questioning: Pose simpler, recall-based questions to struggling learners first, gradually increasing complexity for all students. 8.
2. Remediation (for struggling learners): Simplified Explanations: Re-explain key concepts like periodic law and trends using simpler language and more concrete analogies.
Visual Reinforcement: Provide large, colourful periodic table charts. Use mnemonic devices to remember group names or trends.
Targeted Practice: Assign specific, short exercises focused on identifying groups/periods and recalling definitions, with immediate feedback.
One-on-One Support: Offer individual guidance during activity sessions or after class to address specific areas of difficulty.
Pre-reading/Review Sheets: Provide simplified notes or graphic organizers before the lesson to help them pre-process information. 8.
3. Extension (for high-achieving learners): Research Project: Assign a short research project on the historical development of the periodic table, focusing on the contributions of specific scientists (e.g., Dobereiner, Newlands, Mendeleev, Moseley) or the discovery of specific elements (e.g., noble gases, synthetic elements).
Advanced Trends: Introduce more advanced periodic trends such as effective nuclear charge, metallic bonding strength, or the reasons for anomalies in ionization energy/electron affinity. Quantum Numbers and Electron Configuration: Challenge them to link the periodic table position directly to quantum numbers and more complex electron configurations, including exceptions. * Industrial Case Study: Task them to research a specific Nigerian industry (e.g., cement production, pharmaceutical manufacturing, battery technology) and identify which elements are crucial, how their periodic properties dictate their use, and potential environmental impacts.