Attempt either (a) or (b) :
(a)
(i) Write one example each of one metal that is so soft that it can be cut with a knife, and one non-metal that is a good conductor of electricity.
(ii) Using the electronic configuration, explain how Mg atom combines with oxygen to form magnesium oxide by transfer of electrons. [Atomic number : Mg = 12, O = 8]
Generated by claude-sonnet-4-6 · 2026-06-15 06:46 · grounding rag
Model Answer
(i)
- Metal that can be cut with a knife: Sodium (Na)
- Non-metal that is a good conductor of electricity: Graphite (carbon)
(ii)
Electronic configuration:
- Mg (atomic number 12): 2, 8, 2
- O (atomic number 8): 2, 6
Mg has 2 electrons in its outermost shell. To attain stable configuration, it loses 2 electrons to become Mg²⁺ (2, 8).
Oxygen needs 2 electrons to complete its octet. It gains the 2 electrons from Mg to become O²⁻ (2, 8).
$$\text{Mg} \rightarrow \text{Mg}^{2+} + 2e^-$$
$$\text{O} + 2e^- \rightarrow \text{O}^{2-}$$
The oppositely charged ions (Mg²⁺ and O²⁻) attract each other to form magnesium oxide (MgO).
Source: Chapter 3, Sections 3.1 Physical Properties and 3.3 How do Metals and Non-metals React?
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Explanation
- For (i): Sodium is the textbook example of a soft metal (alkali metals); graphite is the standard exception among non-metals that conducts electricity. Both are directly stated in Section 3.1.
- For (ii): Show the electron configurations clearly, state that Mg loses 2e⁻ and O gains 2e⁻, write the ionic equations, and name the product. Examiners award marks for: correct configurations, direction of electron transfer, ion charges, and naming MgO as the product.