Question 7 The elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively. Which pair of elements belong to the same group?
(a) A and B (b) B and D (c) A and C (d) D and E
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Solution
Option (c) is correct. Elements A and C have electrons in their valence shell. All the elements which belong to the same group should have the same number of valence electrons.