Element B is more reactive because it needs only one electron to attain stability. Both elements are non-metals, so they share electrons to form covalent bonds, resulting in the molecular compound AB3 or PCl3.
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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Element B is more reactive than A because gaining one electron to complete an octet requires less energy than acquiring three electrons. Both A and B are non-metals with high electronegativity, so neither completely transfers electrons. Instead, one atom of A shares three electron pairs with three atoms of B, creating three covalent bonds. The resulting stable covalent compound has the chemical formula AB3.
For more NCERT Solutions of Class 9 Science Exploration Chapter 9 Atomic Foundations of Matter Question Answer (2026-27)
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