Question

What is the oxidation state of chromium in $CrC{l_3}$ ?

Answer 1

The oxidation number of an atom is a number that represents the total number of electrons lost or gained by it. The oxidation state of an atom, a chemical compound, gives information about how many electrons it has lost and so also describes the atom's degree of oxidation.

Complete answer:
In $CrC{l_3}$ , the net charge is $0$.
As Chlorine is more electronegative than chromium, and so it will possess its usual state of $- 1$..
The oxidation state of chlorine is $- 1$.
Let the oxidation state of chromium be $x$.
Then we have,
$x - 3 = 0$
$x = 3$
Therefore, the oxidation number of $Cr$ in $CrC{l_3}$ is $+ 3$ .
The oxidation number of chlorine can be, $- 1,0, + 1, + 3, + 4, + 5$ or $+ 7$depending on the substance containing the chlorine. Chlorine gas has an oxidation number ($C{l_2}$) is zero. Chlorine can have different oxidation numbers in oxide forms.
Chromium belongs to group $6$ of the periodic table .It belongs to the first transition series and therefore known as a transition metal .Its electronic configuration is $[Ar]3{d^5}4{s^1}$.It has $5$ electrons in $3d$ subshell and $1$ electron in $4s$ subshell. Thus, chromium metal has $6$ valence electrons. Thus, the maximum oxidation state of chromium known is $+ 6$.
Chromium has a wide range of oxidation states, with the $+ 3$ state being the most stable. The $+ 3$ and $+ 6$ oxidation states are the most commonly seen in chromium compounds, whereas the $+ 1$, $+ 4$, and $+ 5$ states are rare.

Note:
Due to the property of variable oxidation states, chromium also acts as a catalyst. Chromium forms alloys with metals like iron, nickel and cobalt. The oxidation state of an atom is not considered the atom's real charge. When the oxidation state of a substance increases, it is referred to as oxidation; when the oxidation state decreases, it is referred to as reduction.