Q.Answer the following questions.
Describe the diagonal relationship between Li and Mg with the help of two illustrative properties.

Step 1. Reaction with air. Lithium burns in air to give Li2O plus the nitride Li3N; magnesium burns in air to give MgO plus the nitride Mg3N2. This nitride-forming pattern is typical of group 2, not group 1 — the rest of group 1 (Na, K, …) give only oxide/peroxide/superoxide type products, with no nitride. So here Li behaves like a group-2 element, specifically like Mg.

Step 2. Thermal decomposition of the carbonate. On heating, Li2CO3 decomposes to Li2O + CO2, exactly as MgCO3 decomposes to MgO + CO2. By contrast, the carbonates of the rest of group 1 (Na2CO3, K2CO3, …) are thermally stable and do not decompose under comparable heating. Again, Li's behaviour matches Mg's rather than the rest of its own group. …

Citing two of Table 8.7's illustrative Li–Mg resemblance points and explaining why each …

• Citing a property that's actually true of ALL group 1 elements (not distinctively Li–Mg), which misses the point of a 'diagonal relationship' being about a difference from one's own group. …