3.

Question 1

Explanation to the formation of H2 molecule.

Answer 1

As the two hydrogen atoms approach each other two new attractive interactions & two new repulsive attractions come into play. As attractive interactions are more than repulsive interaction, the atoms come closer with decrease in energy and bond formation takes place at the point of minimum energy.

Question 2

Explanation to the non formation of He2 molecule.

Answer 2

As the number of repulsive interactions (5) is greater than the number of attractive interactions (4), the energy of the system increases and bond formation cannot take place.

Question 3

What is hybridisation?

Answer 3

Intermixing of atomic orbitals belonging to the same atom having slightly different energy so that the redistribution of energy takes place forming new orbitals having equivalent energy and identical shapes.

Question 4

What is a Pi bond?

Answer 4

The type of covalent bond formed by the overlapping of atomic orbitals perpendicular to the internuclear axis.

Question 5

Characteristics of hybridisation are?

Answer 5

1. Only the orbitals belonging to the same atom can undergo hybridisation.
2. The number of hybrid orbitals formed will be equal to the total no of atomic orbitals undergoing hybridisation.
3. Even fully filled orbitals can undergo hybridisation but not bond formation.
4. All the hybrid orbitals irrespective of the type of hybridisation have identical shape but can have different size.
5. Hybrid orbitals overlap to form sigma bonds.

Question 6

sp hybridisation?

Answer 6

one s and one p orbital, BeH2 , linear , 180

Question 7

sp2 hybridisation?

Answer 7

one s and two p orbitals, BH3, trigonal planar, 120

Question 8

sp3 hybridisation?

Answer 8

one s and three p orbitals, CH4 , tetrahedral, 109 28’

Question 9

sp3d hybridisation?

Answer 9

one s, two p and one d orbitals, PCl5, trigonal bipyramidal, 120 and 90

Question 10

sp3d2 hybridisation?

Answer 10

one s, three p, two d orbitals, SF6 , octahedral, 90

Question 11

Hybridisation in NH3?

Answer 11

sp3 hybridisation, 4 hybrid orbitals and 3 overlap with 1s orbital of H, pyramidal , 107

Question 12

Hybridisation in H2O?

Answer 12

sp3 hybridisation, 4 hybrid orbitals & 2 overlap with 1s orbital of H, bent, 104

Question 13

Factors affecting bond length?

Answer 13

1. Size of bonded atoms- directly proportional.
2. Multiplicity of Bonds
3. Type of hybridisation,

Question 14

The size of hybrid orbital increase in the order?

Answer 14

sp<sp2<sp3 (more the percentage of s character smaller the hybrid orbital)

Question 15

Electronegativity and bond length varies in order?

Answer 15

electronegativity-
Csp>Csp2>Csp3
bond length-
Csp<Csp2<Csp3