CBSE Class 10 Science 2017 · Paper 31/1/2/C · Question 5

(i) From left to right in a period, the metallic character of the elements decreases: in Period 3, for example, they change from the metals Na, Mg and Al, through the metalloid Si, to the non-metals P, S and Cl. (ii) Down a group, the metallic character increases. Reason: along a period the nuclear charge increases while electrons enter the same shell, so the valence electrons are held more firmly and lost less readily; down a group new shells are added, so the valence electrons are farther from the nucleus and lost more easily.