NEET Chemistry Notes p-Block Elements – Concept of p-Block Elements
Concept of p-Block Elements
Concept of p-Block Elements
In p-block elements, the last electron enters in the outermost p-orbital. There are six groups of p-block elements in the periodic table, numbering from 13 to 1.8. Their valence shell electronic configuration is ns2np1-6 (except for He). Effective nuclear charge from first to third period decreases and from fourth period and onwards increases, due to poor shielding effect. Therefore, ns2 electrons bound closely to the nucleus. Therefore, the oxidation state two unit less than the group oxidation state becomes progressively more stable in each group. This is also known as inert pair effect.
Variation in Properties of p-Block Elements
- Metallic and Non-metallic Character
Non-metals and metalloids exist only in the p-block of the periodic table. On moving down the group metallic character increases and non-metallic character decreases.
- Multiple Bonding
Second period elements have a tendency to form 
multiple bond (double or triple bond) due to their smaller atomic size and high bond energy, 
- Covalency
Elements of second period do not expand their covalency due to non-availability of d-orbitals. Therefore, halides of such elements do not hydrolysed easily, e.g. BC13, CC14 (halides) etc. While elements of third period and onwards only form single bond and can expand their covalency due to presence of vacant d-orbitals, e.g. P4, S8, [A1F6]3 ion etc.
- Nature of Oxides
Non-metal oxides are acidic or neutral and metal oxides are basic in nature. Generally metalloid oxides are amphoteric. In a period, from left to right acidic character increases and down a group, basic character increases. Generally oxides with higher oxidation state are more acidic in nature.
Unique Behaviour of the First Element in Each Group
It is due. to the
- small size
- high electronegativity and
- non-availability of d-orbitals in the valence shell of first element in each group.