Question

The oxidation number of chromium in \[{K_2}C{r_2}{O_7}\]?
A) \[2 + \]
B) \[3 + \]
C) \[6 + \]
D) \[8 + \]

Answer 1

Hint: We need to know that potassium dichromate is an ionic compound consisting of two potassium cations and one dichromate anion. The coordination geometries around the chromium atoms are tetrahedral. Oxidation number is also called oxidation state, the total number of electrons that an atom either gains or losses in order to form a chemical bond with another atom.

Complete answer:
We will solve this question step by step:
Potassium exhibits an oxidation state of \[ + 1\], oxygen exhibits an oxidation state of \[ - 2\]
So, the total charge of potassium ions is \[ + 1\] \[(2)\]=\[ + 2\], while oxygen ions is \[ - 2\left( 7 \right) = - 14\].
Let x be the oxidation number of two chromium atoms.
Hence we can write the equation as
\[2 + x - 14 = 0\]
\[ - 12 + x = 0\]
$x = 12$
So, two chromium atoms have an oxidation number of \[ + 12\].
So one chromium atom will have an oxidation number of \[\dfrac{{ + 12}}{2} = + 6\]
So the oxidation number of $Cr$ in \[{K_2}C{r_2}{O_7}\] is \[ + 6\].
Hence in the molecule potassium exhibits an oxidation state of \[ + 1\], oxygen exhibits an oxidation state of \[ - 2\] and chromium exhibits an oxidation state of \[ + 6\].
Oxidation number is also referred to as oxidation state. However, sometimes these terms can have a different meaning depending on whether we are considering the electronegativity of the atoms or not. The oxidation number term is used frequently in coordination chemistry.

Option C is the correct answer.

Note:
We have to know that the oxidation number in simple terms can be described as the number that is allocated to elements in a chemical combination. The oxidation number is basically the count of electrons that atoms in a molecule can share, lose or gain while forming chemical bonds with other atoms of a different element.