CBSE Class 12 Chemistry Notes: The p Block Elements – Introduction

The right side of the periodic table having group number 13, 14, 15, 16, 17 and 18 are known as p – block elements. These elements have 3, 4, 5, 6, 7 and 8 electrons in their outer most shell, respectively. The last electron of these groups’ elements occupies the position in p – sub shell that is why are added as p – block elements. Their general configuration is ns2np1-6.

Some important properties of p-block

(1) Electron affinity
Electron affinity increase from left to right along the period amongst the p – block elements and it decreases from top to bottom. But group 15 is having exceptionally low values of electron affinity and is due to extra stability because of the presence of exactly half filled orbital in their valence shell. Similarly, elements of group 18 (noble gases) have zero affinities due to presence of complete octet which provides then stability.

(2) Metallic Character
The metallic character is governed by
(i) Size of atoms and
(ii) Ionization energy.
The elements having bigger size and low ionization energy has a greater metallic character. After combining both above mentioned factors we observe that the elements with above two properties are located in left corner of p – block and strong non – metallic elements are located at right corner and a diagonal strip of elements separates thus two, having in between properties are called as metalloids.

(3) Oxidation state
The p – block elements show variety of oxidation states both positive and negative. Some of the p – block elements show different oxidation state due to inert – pair effect, where their lower oxidation state is more predominant.

Some important characteristics of p – block in tabular form

The p Block Elements

Illustration 1.
Which of the following arrangements represent the correct order of electron affinity of the given atomic species?
(A) F < Cl < O < S (B) S < O < Cl < F
(C) O < S < F < Cl (D) Cl < F < S < O
Solution: (C)

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