Question

The oxidation state of aluminium is ________
(A) +3
(B) +1 and +3
(C) +2 and +3
(D) +1

Answer 1

Hint: Oxidation state refers to the number of electrons a compound may gain or lose in order to achieve a stable electronic configuration, i.e. configuration of its nearest noble gas. Atomic number of Aluminium is 13.

Complete step by step answer:
- Aluminium is a p-block element with atomic number equal to 13. It is placed in period 3 and group 13 of the modern periodic table.
- The electronic configuration of aluminium is $[Ne]3{{s}^{2}}3{{p}^{1}}$.
As we can see, aluminium has 3 electrons in its valence shell (third shell). Aluminium can easily lose three electrons to gain the electronic configuration of Neon. Therefore, its oxidation state = +3 is most stable.
- Aluminium shows oxidation state of +1 and +2 in some compounds, but it is not very stable.
Therefore, the answer is – option (a) – The oxidation state (most stable) of aluminium is +3.

Additional Information: Elements placed in group 13 of the modern periodic table are known as elements of the boron family. It is because the first element of group 13 is Boron.

Note: The oxidation number of an atom or element is a number that indicates the total number of electrons lost or gained by it. There are certain rules for calculating oxidation number –
- Oxidation number of any free element is zero.
- Oxidation number for a monatomic ion is equal to the net charge on it.
- Hydrogen, in general, has an oxidation state equal to +1. However, it is -1 in forms of a compound with an element with lesser electronegativity.
- Alkali metals have oxidation number = +1
- Alkali earth metals have oxidation number = +2
- Halogens have oxidation number = -1
- Oxygen has an oxidation number = -2, but in case of peroxides, it is -1.