Test: Molecular Orbital Theory (NCERT)

The atomic orbitals of comparable energies combine to form molecular orbitals

An atomic orbital is monocentric while a molecular orbital is polycentric

Bonding molecular orbital has higher energy than antibonding molecular orbital

Molecular orbitals like atomic orbitals obey Aufbau principle for filling of electrons

2

4

8

6

The combining atomic orbitals must have nearly same energy

The combining atomic orbitals must overlap to maximum extent

Combining atomic orbitals must have same symmetry about the molecular axis

Pi (π) molecular orbitals are symmetrical around the bond axis

(σls²) (σ*1s²) (σ2s²) (σ*2s²) (σ2p²_z) (π2p²_x)

(σls²)(σ*1s²) (σ2s²) (σ*2s²) (π2p²_x = π2p²_y)

(σls²) (σ*1s²) (σ2s²) (σ*2s²)(σ2p²_z)(π2p¹_x = π2p¹_y)

(σls²) (σ*1s²) (σ2s²)(σ*2s²) (π2p¹_x = π2p¹_y)

C₂

B₂

O₂

Be₂

N₂

F₂

O^-₂

O^2-₂

N₂ > N⁺₂ = N⁻₂ > N²⁻₂ 

N⁺₂ > N⁻₂ > N₂ > N²⁻₂ 

N⁻₂ > N⁺₂ > N₂ > N²⁻₂

N²⁻₂ > N⁻₂ = N⁺₂ > N₂

One

Two

Three

Zero

Zero bond order

Negative bond order

Positive bond order

All of these

F₂ and O^2-₂

N₂ and CO₂

O₂ and O^-₂

N₂ and N⁺₂ 

2.5, 2.5 and 3 respectively

2,2.5 and 3 respectively

3, 2.5 and 3 respectively

2.5, 2.5 and 2.5 respectively

H⁺₂

Be₂

B₂

C₂

Bond order is given by the number of bonds between the two atoms in a molecule

With increase in bond order, bond enthalpy of the molecule decreases

Isoelectronic molecules and ions have identical bond orders

With increase in bond order, bond length decreases

N_b > N_a,B.O.= +ve

a

b

c

d