UPSC Combined Geo-Scientist, Mains · 2019 · Mains Paper I

Q1(c). Diagonal relationship

Question

Illustrate diagonal relationship with an appropriate example.

Diagonal neighbours in periods 2 and 3 can show similar chemistry; Li and Mg are a standard example.

Across a period ionic radius decreases while charge density and electronegativity generally increase.
Li and Mg form nitrides on direct combination: 6Li + N₂ → 2Li₃N; 3Mg + N₂ → Mg₃N₂.
Their carbonates decompose on heating to oxides and CO₂, and their nitrates also give oxides rather than the nitrite pattern typical of sodium.

The full model answer

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CoversDiagonal relationshipPeriodic trends