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# Find oxidation number of boron in $NaB{H_4}$

Last updated date: 16th Jul 2024
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Hint: Boron is a chemical element with atomic number 5 and the letter B. It is a low-abundance element in the Solar System and the Earth's surface, generated entirely by cosmic ray spallation and supernovae rather than stellar nucleosynthesis. It makes up about 0.001% of the Earth's crust by weight.

In basic terms, the oxidation number is the number assigned to the elements in a chemical mixture. The oxidation number is the total number of electrons that atoms in a molecule will share, lose, or obtain when forming chemical bonds with atoms of another substance.
Rules for Assigning Oxidation Numbers
It is customary to write the action first in a formula, followed by the anion.
A free element's oxidation number is always zero.
The charge of a monatomic ion is equal to its oxidation number.
Hydrogen's oxidation number is typically +1. In materials containing elements that are less electronegative than hydrogen, the oxidation number of hydrogen is -1.
In certain compounds, the oxidation number of oxygen is -2 except in fluorides.
A Group IA member in a compound has an oxidation number of +1.
A Group IIA member in a compound has an oxidation number of +2.
Except when paired with a higher electronegativity factor, the oxidation number of a Group VIIA element in a compound is -1. In HCl, Cl has an oxidation number of -1, but in HOCl, it has an oxidation number of +1.
The oxidation numbers of all the atoms in a neutral substance add up to zero.
The charge of a polyatomic ion is proportional to the sum of its oxidation numbers.
Now in $NaB{H_4}$
A Group IA member in a compound has an oxidation number of +1.
Na = + 1
Since this is a metal hydride, hydrogen's oxidation state is - 1.
$H_4 = 4 \times (-1) = -4$
Hence $NaB{H_4}$ = 1 + x – 4 = 0
X = 3
Oxidation number of Boron = 3

Note:
The inorganic compound sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, has the formula NaBH₄. This white solid, which is generally found as a powder, is a reducing agent used in chemistry, both in the laboratory and on a large scale.