Question

Two elements $X$ and $Y$ belong to Groups $1$ and $2$ respectively in the same period of the Periodic Table. Compare these elements with respect to :
(i) Number of electrons in their outer-most orbit.
(ii) Their atomic size and their valencies.
(iii) Their ionisation energy and metallic character.
(iv) Formulae of their chlorides and sulphates.

Answer 1

(i) X has 1 electron in its outermost orbit whereas $Y$ has 2 electrons. Number of outermost electrons in obtained from the group number.

(ii) Atomic size decreases across the period, thus $X$ has higher atomic size.

(iii) Ionsation energy decreases across the period and metallic character increases so, X has higher ionisation energy but lower metallic character.

(iv) Chlorides: $XCl$ and $YC{l}_2$

Sulphates: $X_{2}S{O}_4$ and $YS{O}_4$.