chemistry 12th class cbse notes

Atomic and Ionic Radii

  • Covalent and ionic (in a particular state) radii increase in size down the group.
  • There is a considerable increase in covalent radius from N to P.
  • However, from As to Bi only a small increase in covalent radius is observed. This is due to the presence of completely filled d and/or f orbitals in heavier members.

Ionization Enthalpy

  • Ionisation enthalpy decreases down the group due to gradual increase in atomic size. Because of the extra stable half-filled p orbitals electronic configuration and smaller size, the ionisation enthalpy of the group 15 elements is much greater than that of group 14 elements in the corresponding periods.
  • The order of successive ionisation enthalpies, as expected is ΔiH1 < ΔiH2 < ΔiH3 (above table).


  • The electronegativity value, in general, decreases down the group with increasing atomic size.
  • However, amongst the heavier elements, the difference is not that much pronounced.

Metallic Character

  • Group 15 elements are less metallic.
  • Metallic character increases down the group.
  • Nitrogen and phosphorus are non-metals, arsenic and antimony metalloids and bismuth is a metal.

Melting and Boiling Point

  • The boiling points, in general, increase from top to bottom in the group.
  • The melting point increases up to arsenic and then decreases upto bismuth.


  • Except for nitrogen and bismuth, all the elements show allotropy
  • All the elements of this group are polyatomic.
  • Dinitrogen is a diatomic gas while all others are solids.

How useful was this post?

Click on a star to rate it!

Average rating 4.4 / 5. Vote count: 7

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post? Please mention your Email so that we can contact you for better feedback.


Please enter your comment!
Please enter your name here