Question

which of the following molecules has bond order 2.5? (a) Hcl (b) CO (c) NO (d) CO2

Answer 1

Answer...........

HCL

Answer 2

Concept:

In molecular orbital theory, bond order is equal to the difference, divided by 2, between the number of bonding and antibonding electrons.

Given:

(a) HCl (b) CO (c) NO (d) CO₂

Find: Which of the following molecules has bond order 2.5?

Solution:

It can be calculated as:

Bond order = $\frac{number of electrons in (bonding molecular orbital - antibonding molecular orbital)}{2}$

In the MOT diagram of HCl,

• The number of electrons in bonding molecular orbital = 2
• The number of electrons in antibonding molecular orbital = 0
• Bond order = $\frac{2-0}{2}$ = $\frac{2}{2}$ = 1

In the MOT diagram of CO,

• The number of electrons in bonding molecular orbital = 6
• The number of electrons in antibonding molecular orbital = 0
• Bond order = $\frac{6-0}{2}$ = $\frac{6}{2}$ = 3

In the MOT diagram of NO,

• The number of electrons in bonding molecular orbital = 6
• The number of electrons in antibonding molecular orbital = 1
• Bond order = $\frac{6-1}{2}$ = $\frac{5}{2}$ = 2.5

In the CO₂, each carbon possesses 1 sigma bond and 1 pi-bond. Thus, it has a bond order of 2.

Hence, the NO molecule has a bond order of 2.5.

The correct option is (c) NO.

#SPJ2