Question

Based on formal charges, draw the most preferred Lewis structure for ClO3-?

Draw the molecule by placing atoms on the grid and connecting them with bonds. Include lone pairs of electrons an formal charges.

Answer 1

Concepts and reason

Calculate the formal charge of an atom in a molecule by using the following formula.

Formalchargeofatom = Numberofvalanceelectrons - [Numberofunsharedvalance

electrons $+\frac{1}{2}$ Numberofsharedvalanceelectrons $]$ Draw the most preferred Lewis structure based on the formal charges.

Fundamentals

Charge on an atom without considering electronegativity differences is called a formal charge. Lewis structure shows bonding between atoms present in a molecule, lone pair of electrons can also be placed on the atoms.

A pair of valance electrons that do not involve in the chemical bond is called a lone pair of electrons.

 

The molecule is $\mathrm{ClO}_{3}^{-}$ The ion has one chlorine and three oxygen atoms. The central atom of the ion is chlorine. The negative charge on the ion is shared with one of the oxygen atoms. Based on the valances of the atoms, they are connected as shown below.

Calculate formal charge of double bonded oxygen atom. Formalcharge $=6-\left[4+\frac{1}{2} \times 4\right]=0$

Calculate formal charge of negatively charged oxygen atom as shown below. Formalcharge $=6-\left[6+\frac{1}{2} \times 2\right]=-1$

The formal charge on the chlorine atom is as follows:

Formalcharge $=7-\left[2+\frac{1}{2} \times 10\right]=0$

Explanation | Hint for next step

Oxygen belongs to group 6 A of the periodic table. Thus, the valance electrons of the oxygen atom are 6. The singly bonded oxygen has two shared electrons and 6 unshared electrons. The double-bonded oxygen has four shared electrons and 4 unshared electrons.

 

Based on the formal charges of the chlorine and oxygen atoms, Lewis structure for $\mathrm{ClO}_{3}^{-}$ can be drawn as shown below.

The most preferred Lewis structure for $\mathrm{ClO}_{3}^{-}$ is as follows:

Formal charges of chlorine, negatively charged, and double-bonded oxygen is $0,-1,$ and 0 respectively. They can be indicated as shown below.