Question

The atomic radii of group 1 elemetns of the periodic table are as follows:
`Na (186 "pm"), Li (152 "pm"), R(244"pm"),Cs(262"pm")` and `K(231"pm")`.
(a) Arrange these element in the increasing order of their atomic radii in a vertical column (keeping the element with the smallest atomic radius at the top).
(b) Which elements have the smallest and largest atoms?
(c) From this data, infer how the size (or atomic radius) of elements vary as we go doen in the group

Answer 1

(a) In this problem, the smallest atoic radius 152pm is of `Li` so `Li` should be placed at the top of the group (as shown in the table alongside). This is followed by `Na (186"pm"),K(231"pm"),Rb(244"pm")` and `Cs(262"pm")` in the downward direction.
(b) The element `LI` (Lithium) has the smallest atom (atomic radius 152 pm) whereas the element `Cs` (Cesium) has the largest atom (atom radius 262 pm).
(c) From this arrangement of elements we conclude that the atom size (or atomic radius) of elements increases on going down in a group.