The properties which shows gradual variation in a group and
in a period. They are repeat themselves after a certain
interval of time.
VALENCY:-
It is determined by number of valence electrons present in the
outermost shell of an atom.
All elements of a group have same number of valence
electrons.
They have same valency.
Valency increases from 1 to 4 second for 2nd and 3rd period.
Valency decreases from 4 to 0 when we go from left to right in
the table.
ATOMIC SIZE:-
It is determined by atomic radius.
For an isolated atom, atomic radius is the distance between
the center of atom and outermost shell.
Atomic radius decreases from left to right.
Atomic radius increases from top to bottom.
Increase and decrease is happen because of adding electrons.