p-block Elements part-II

The p-block Elements

Elements belonging to groups 13 to 18 of the periodic table are called p-block elements.

Their general electronic configuration is ns 2 np 1 – 6. The s-orbitals

of these elements are complete whereas the p-orbitals are progressively filled. The properties of these elements are dependent upon the electrons present in p-orbitals.

Some characteristics of p-block elements summarized for a quick reference :

1.Atomic and Ionic Radii. The size of an atom is expressed in terms of atomic radius, van der Waal's radius or covalent radius. The atomic radii of p-block elements decrease on moving from left to right in a given period and increases from top to bottom in any group.

2. Ionization Enthalpy. The ionization enthalpy of p-block elements increases from left to right in a period and decreases on descending a group. However, the ionization energy of group 13 elements is found to be smaller than the group 2 elements (Alkaline earths).

3. Electron Gain Enthalpy. Electron gain enthalpy increases from left to right along a period amongst the p-block elements. It value decreases from top to bottom in a particular group.

4. Electronegativity. It is the property of an atom in a molecule. It refers to the tendency of an atom to pull the shared pair of electrons towards itself. It depends upon

(i)size of atom and

(ii) electrons needed complete the valency shell.

In general, the electronegativity increases from left to right along the period and decreases from top to bottom in a group. The difference of electronegativities between the two atoms gives us an idea about the kind of bond set up between two atoms.