Question

What is the oxidation state of bromine in \[AlB{r_3}\] ?
A)-1
B)+3
C)0
D)-3

Answer 1

Hint: While calculating the oxidation states of atoms in a compound, first understand the net charge on the compound and then keep this value in the LHS of the equation. Now determine the elements with fixed oxidation states and multiply this number with the number of these atoms present. Then assume the oxidation states of the remaining numbers to be variables and multiply them with the number of the atoms present. Put this entire value in the RHS of the equation.

Complete Step-by-Step Answer:
Before we move towards the solution of this question, let us understand some basic concepts.
1)Oxidation number or oxidation state of an element can be defined as the degree of oxidation of an element in a given compound. In simpler terms, it can be understood as the number of the electrons gained or lost by an atom while forming a compound. This results in forming a net charge over this element, which is referred to as the oxidation state.
2)Depending on the number of electrons present in the valence shell of an atom, an element may exhibit a single or in some cases multiple oxidation states, depending on the atoms they are combining with.
Now, forming the equation for calculating the oxidation state of bromine in \[AlB{r_3}\] :
Net charge on \[AlB{r_3}\] = (O.S. of aluminium) (no. of atoms of aluminium) +
             (O.S. of bromine) (no. of atoms of bromine) +
 \[0 = \left( x \right)\left( 3 \right) + \left( { + 3} \right)\left( 1 \right)\]
 \[0 = \left( x \right)\left( 3 \right) + \left( { + 3} \right)\left( 1 \right)\]
 \[0 = 3x + 3\]
 \[ - 3 = 3x\]
 \[x = - 1\]
Hence, the oxidation state of bromine in \[AlB{r_3}\] is \[\left( { - 1} \right)\]
Hence, Option A is the correct option

Note: Bromine belongs to the halogen group of elements. All the elements in this group have 7 electrons in their valence shell. Hence, they have the capacity to take in only one electron to satisfy their octet. Hence, elements in the halogen group do not exhibit multiple oxidation states, but exhibit only one oxidation state of \[\left( { - 1} \right)\]