Question

The correct order of atomic radii for the following species is $Na,Li,Rb,$ and $K$ is:

• A.
  $Li>Na>K>Rb$
  
• B.
  $Rb>K>Na>Li$
• C.
  $Na>Li>K>Rb$
• D.
  $Rb>K>Li>Na$

Answer 1

The correct option is B

$Rb>K>Na>Li$
Atomic radius is the distance from the centre of the nucleus to the outermost shell containing electrons. In other words, it is the distance from the center of the nucleus to the point up to which the density of the electron cloud is maximum.
The atomic radius increases as we move down the group due to the increase in number of shells.
Hence, the correct order is B i.e,$Rb>K>Na>Li$