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Question
(a) How is possible valency of an element determined from the electronic configuration of its atom ?
(b) Determine the valency of an element X whose atomic number is 15.
Solution
(a) Valency can be determined from no. of electron in the outermost shell. No. of electron in the outermost shell can be observed by writing the electronic configuration.
(b) X : 2, 8, 5
15
Element X has 5 electron in the outermost shell, hence the valency of is 8–5= 3.
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