CBSE Class 10 Science 2017 · Paper 31/1/1 · Question 9

Vertical columns: groups (18 in all). Horizontal rows: periods (7 in all). Metallic character increases on moving down a group. Reason: a new shell is added at each step down, so the valence electrons are farther from the nucleus and the effective nuclear charge they experience decreases; they are therefore lost more easily, and the tendency to lose electrons is what metallic character is. Atomic radius decreases on moving from left to right along a period. Reason: the nuclear charge increases by one unit at each step while the electrons are added to the same outermost shell, so the greater nuclear charge pulls the electrons closer to the nucleus and the atom becomes smaller.