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. Write the formula of and mention the nature of the compound formed by the union of 19K and element X(2, 8, 7).

Answer 1

i) fluorine has 1 electron in outermost shell

ii) K and F are of same group

iii) KX (KCl) will be formed

Answer 2

(i) Potassium (19 K)
(ii) Beryllium (Be 4) and Calcium ( Ca 20)

K         Cl
1   ↔    1     (valency)
⇒ KCl  Potassium chloride forms