Question

Arrange the following atoms in order of increasing radius (With reason ) :
1) Cr ,Mn ,Fe
2) Ni ,Cu ,Zn
3) Ge , As , Se
4) Tl , Zr , Hf

Answer 1

(1) Cr>Mn>Fe bcz nuclear charge> screening effect
(2) Zn>Cu>Ni bcz nuclear charge<screening effect.
(3) Ti<Zr=Hf due to lanthanoid contraction...
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Answer 2

1) in 4th peroid , atomic radius decreases upto Ni then increases from Cu to Ga and again decreases .
so, Cr> Mn > Fe

2) Ni < Cu < Zn

3) Ge >As > Se

4)exception is the 4th period ( Ti , Zr, Hf)
due to lanthanide contraction ,there is a slight increases or almost no increases in atomic radius from 5th to 6th period in transition metals .
Ti < Zr ≈ Hf