Four elements P, Q, R and S have atomic numbers 12,13,14 and 15 respectively

Four elements P, Q, R and S have atomic numbers 12,13,14 and 15 respectively.
Answer the following questions giving reasons:
(i) What is the valency of Q ?
(ii) Classify these elements as metals and non-metals.
(iii) Which of these elements will form the most basic oxide ?

(i) 3 (+3)
(ii) P and Q are metals while S is a non-metal, R is a metalloid.
(iii) P (because they are in same period and metallic character decreases in a period due to increase in the nuclear charge).