Question

how elements of first group have large charge/radius ratio

Answer 1

Elements of the First Group: (ns​¹)
Li
Na
K
Rb
Cs

They all form mono positive cation M⁺. As we know that Group 1 metals are largest in size in the periodic table. When they form cation their size decreases but still form a larger cation and as we go down the group,size increases due to increase in number of shells.So,as they have a large size,they have a large radius. Thus,

Charge to radius ratio = $\frac{Charge}{Radius}$


As the radius is more,they have small charge to radius ratio,not large.