Question

Consider the following elements (atomic numbers are given in parenthesis)

Ca(20); K(19); F(9); Be(4)

(a) Select:

(i) the element having one electron in the outermost shell.

(ii) two element of the same group. Write the number of this group.

(b) Write the formula of the compound formed by the union of Ca(20) and the element X(2,8,7).

Answer 1

(a) (i) K (Potassium-2,8,8,1)

(ii) Be and Ca in the same group because both have same number of valence electrons in their outermost shell.

(b) Ca     X

Valency 2    1

Ca₁X₂ =CaX₂