A co-ordinate bond is formed by ______.

1

(a)

sharing of electrons contributed by both the atoms

(b)

complete transfer of electrons

(c)

sharing of electrons contributed by one atom only

(d)

none of these

The species CO, CN^- and N₂ are ______.

1

(a)

isoelectronic

(b)

having coordinated bond

(c)

having polar bond

(d)

having low bond energies

The molecule Ne₂ does not exist because ______.

1

(a)

N_b > N_a 

(b)

N_b = N_a

(c)

N_b < N_a

(d)

None of these

Which one is diamagnetic among NO⁺ , NO and NO^-?

1

(a)

NO⁺

(b)

NO

(c)

NO^-

(d)

None of these

sp³, sp² and sp hybridized carbon atom, the p character is maximum in:______.

1

(a)

sp³ 

(b)

sp²

(c)

sp

(d)

all of the above have same p-character

What type of  atomic orbitals  can overlap to form molecular orbitals?

1

(a)

Atomic orbitals  with comparable energies and proper orientation overlap to form molecular orbitals

Can we have a diatomic molecule with its ground state molecular orbitals full with electrons? Give a reason for your answer.

1

(a)

No, because bond order becomes zero, e.g in case of He₂, Be₂, Ne₂ etc. Note that in H₂ ,\(\sigma 1s\) molecular orbitals is full but  \(\sigma 1s\) is empty.

Use molecular orbital theory to explain why the Be₂ molecule does not exist.

1

(a)

Electronic configuration of Be₂ molecule (4 + 4 = 8) 
\({ \sigma 1s }^{ 2 },{ \sigma 1s }^{ 2 },{ \sigma 1s }^{ 2 },{ \sigma 1s }^{ 2 }\)
\(Bond \ order=\frac { 1 }{ 2 } [{ N }_{ b }-{ N }_{ a }]=\frac { 1 }{ 2 } (4-4)=0\)
Since, bond order in zero, so Be₂ does not exist.

What is valence bond approach for the formation of covalent bond?

1

(a)

A covalent bond is formed by the overlap of half-filled atomic orbitals.

Out of \(\sigma \) and \(\pi \)-bonds, which one is stronger and why?

1

(a)

\(\sigma \) bond is stronger. This is because  \(\sigma \)-bond is formed by head-on overlapping of atomic orbitals and therefore, the overlapping is large.  \(\pi \) -bond is formed by sideway overlapping which is small.

How is bond order related to bond length of a molecule?

1

(a)

Bond length is inversely proportional to bond order.

Define antibonding molecular orbital.

1

(a)

The molecular orbital fonned by the subtractive effect of the electron waves of the combining atomic orbitals, is called antibonding molecular orbital.

Arrange the bonds in order of increasing ionic character in the molecules: LiF, K₂O , N₂, SO₂ and ClF₃ .

1

(a)

Arrange the following bonds in order of increasing ionic character giving reason. N-H, F-H, C-H and O-H

1

(a)

Arrange the following in order of decreasing bond angles.
(i) CH₄, NH₃, H₂O, BF₃, C₂H₂
(ii) \({ NH }_{ 3 },{ NH }_{ 2 }^{ - },{ NH }_{ 4 }^{ + }\)

1

(a)

Why B₂ is paramagnetic in nature while C₂ is not?

3

(a)

The molecular orbital electronic configuration of both B₂ and C₂ are.
B₂: [σ1s]² [σ*1s]² [σ2s]² [σ*2s]² [\(\pi\) 2px]¹ [\(\pi\)2y]¹
C₂: [σ1s]² [σ*1s]² [σ2s]² [σ*2s]² [\(\pi\) 2px]² [\(\pi\)2y]²
Since, B₂ has two unpaired electrons, B₂ is paramagnetic.
C₂ has no unpaired electron. Thus, C₂ is diamagnetic

Explain the diamagnetic behaviour of F₂ molecule on the basis of molecular orbital theory

3

(a)

Arrange the following sets of molecules in the decreasing order of bond angle.
(a) SF₆, CCl₄, H₂O, NH₃
(b) CH₄, NH₃, H₂O, BF₃

3

(a)

Explain the formation of H₂ molecule on the basis of valence bond theory.

3

(a)

Explain why BeH₂ molecule has a zero dipole moment although the Be–H bonds are polar.

5

(a)

the percentage ionic character in certain bond A-B is 54.76% and the bond length A-B is given as 246 \(\mathring { A } \). What is the dipole moment of AB molecule?

5

(a)

Apart from tetrahedral geometry, another possible geometry for CH₄ is square planar with the four H atoms at the corners of the square and the C atom at its centre. Explain why CH₄ is not square planar ?

5

(a)