Question 13 — Two elements, A and B, - Questions at the end of the chapter - Chapter 9 - Atomic Foundations of Matter (Exploration)

Last updated at July 20, 2026 by

Question 13
Two elements, A and B, have the following configurations — A: 2, 8, 5   B: 2, 8, 7 (i) Which element is more reactive? (ii) Will A and B form ionic or covalent bonds when they combine? Explain using electron transfer or sharing. (iii) Predict the formula of the compound they would form.
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  • (i) B is more reactive — it needs only 1 electron to complete its octet.
  • (ii) A has 5 valence electrons and B has 7; both are non-metals, so they share electrons → a covalent bond.
  • (iii) A needs 3 electrons and B needs 1, so the formula is AB₃ .
A (2,8,5) and B (2,8,7) B is more reactive Both non-metals, so they share Covalent bond, formula AB3
Back to: 9.4.2 Bonding by electron transfer — Ionic bond
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