Question

What is the oxidation state of chromium in \[C{r^{2 + }}\]?
A) \[ + 2\]
B) \[ - 2\]
C) $0$
D) \[ + 1\]

Answer 1

Hint: We have to remember that the oxidation state is the charge on a particular atom or element. Oxidation state tells us how many numbers of electrons are being added to or removed from a species. We also remember that the oxidation state can be positive or negative integers and also it can be zero.
For example: \[N{a^ + }\]has an oxidation state of \[ + 1\].

Complete step by step answer:
We must remember that the oxidation can also be said that it is the total charge on a particular atom after heteronuclear bonds approximation.
\[C{r^{2 + }}\]has an oxidation state\[ = + 2\]
As we know that the chromium has an atomic number which is 24 and an atomic symbol as \[Cr\].
Electronic Configuration of\[Cr\]: \[\left[ {Ar} \right]3{d^5}4{s^1}\]
\[C{r^{2 + }}\]means that this atom has lost 2 electrons to attain this electron configuration, due to which its oxidation state comes out to be 2.

Electronic configuration of\[C{r^{2 + }}\]: \[\left[ {Ar} \right]3{d^4}\]
Option A) this is a correct option as \[C{r^{2 + }}\] has an oxidation state of \[ + 2\].
We can look at an example to understand this well.
\[Cr{O_4}^{2 - }\], \[ + 2\] is added to the oxidation states of \[Cr\] and \[O\] because the total charge on chromate ion \[Cr{O_4}^{2 - }\]is \[ - 2\] which is its oxidation state also.
Option B) this is an incorrect option as \[ + 2\] is the correct answer.
Option C) this is an incorrect option as $0$ is the oxidation state for \[Cr\] atoms and not\[C{r^{2 + }}\].
Option D) this is an incorrect option.

Hence, the correct option, ‘Option A’.

Note: We have to know that the oxidation state of a neutral atom i.e. \[Cr\] which has no charge on it is also known as ground state as it has $0$ oxidation state.