Arrange the following elements according to the instructions written in paranthesis.

(i) Cu, Mn, Ge, Sc (increasing atomic size)

(ii) Fe, Hs, Ru, Os (increasing number of valence shells)

(iii) Hf, Cs, Ba, Tl (increasing valency)

(i) Cu, Mn, Ge, Sc all belong to same period. The order in which they appear in the period in left to right direction is: Sc → Mn → Cu → Ge. The atomic size decreases on moving along a period. This is because of the increase in the effective nuclear charge on moving from left to right which tends to pull the electrons towards the nucleus. Therefore, the increasing order of atomic sizes is: Ge < Cu< Mn< Sc.

(ii) Fe, Hs, Ru, Os all belong to the same group. On moving down a group, the number of shells increases. Thus the increasing order for number of shells is Fe<Ru<Os<Hs.

(iii) Number of valence electrons in given elements is as follows:

Hf → 4

Cs → 1

Ba → 2

Tl → 3

So the order for increasing valency is : Cs<Ba<Tl<Hf