chemistry

OXIDATION STATES

The charge which an atom appears to be possessed in a molecule or ion is called its oxidation state. Oxidation state may be positive or negative or a fraction or zero.

For s-block elements oxidation number is equal to the group number.

p-block elements show different oxidation states which often differ by 2 units.

The s-electron pair in the valence shell of the heavier elements of p-block show reluctance in bond formation. This is called inert pair effect.

In p-block group III elements have a common oxidation state of +3.

For thallium + 1 oxidation state is more stable than + 3 oxidation state, due to inert pair effect. Group IV elements show + 4 and +2 oxidation states.

Group V elements show + 5 and +3 oxidation states.

The common oxidation state shown by group VI elements is –2.

The other oxidation states shown by VI group elements are + 2, +4 and +6.

Halogens are the most electronegative elements and show the common oxidation state –1. Fluorine always shows the oxidation state–1.

The other halogens show positive oxidation state +1, +3, +5 and +7. The common oxidation state of transition or

d-block elements is +2 due to the ns²electronic configuration.

Ruthenium (Ru) and osmium (Os) show the highest oxidation state of +8. Carbon show the lowest oxidation state of–4.

f-block elements or inner transition elements show the common oxidation state of +3. The highest oxidation state shown by any element is equal to its group number.