Question

From the following elements : 4Be; 9F; 19K; 20Ca (i) Select the element having one electron in the outermost shell. (ii) two elements of the same group.

Answer 1

The valence electron of $Be_{4}$ = 2.
The valence electron of $F_{9}$ = 7
The valence electron of $K_{19}$ = 1
The valence electron of $Ca_{20}$ =2

The two elements of the same group is Be and Ca.

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