Chemical Bonding

Question 1

What is an electrovalent bond

Answer 1

Bond between two atoms held by electrostatic force due to complete transfer of electron

Question 2

How to calculate the heat of formation

Answer 2

sublimation energy + dissociation energy/2 + ionization enthalpy - electron affinity - lattice energy

Question 3

What is lattice energy

Answer 3

The energy released when one mole of a crystalline solid is formed when oppositely charged particles gets packed closely

Question 4

What are the factors of lattice energy

Answer 4

size of the ion, charge of the ion

Question 5

What is an ionic crystal

Answer 5

A three dimensional aggregate formed when oppositely charged ions are arranged in a regular continuous geometrical pattern

Question 6

What are the reasons for variable valency

Answer 6

1. Unstable electronic configuration
2. Inert pair effect

Question 7

Explain the role of unstable electronic configuration in variable valency

Answer 7

Transition metals need to lose many electrons to attain octet. After losing a few though, due to an increase in nuclear charge, more electrons are not lost

Question 8

Explain the role of inert pair effect in variable valency

Answer 8

S-electrons penetrate closer to the nucleus, hence they require more energy to be removed. this causes variable valency

Question 9

How does inert pair effect vary down a group

Answer 9

It increases. In a covalent bond down a group, the bond strength decreases due to the large distance between the atoms. The energy due to the bond isn’t enough to excite the s-electrons so they do not take part

Question 10

What is covalent bond

Answer 10

A bond formed by the mutual sharing of electrons between two atoms

Question 11

What are isomorphs

Answer 11

the are crystalline compounds with similar arrangements of atoms and geometry

Question 12

What are the exceptions to the octet rule

Answer 12

1. Hydrogen and Helium
2. Couldn’t explain electron deficient like BeCl2, BF3
3. Could not explain PF5, IF7, which have more than 8 e
4. Failed to explain why inert gases form compound
5. Odd electron bonds

Question 13

Explain why the octet rule failed

Answer 13

1. Sidgwick’s max covalence rule - the max covalency of an element is limited according to the period
2. Sugden’s view of singlet linkage - an element having octet could share one electron
3. Atoms can use vacant d orbital to expand their octet

Question 14

What is sigma bond

Answer 14

A bond formed by head-on overlapping of orbitals along the internuclear axis
Strong, symmetrical, free rotation

Question 15

What is pi bond

Answer 15

Bond formed by sideways overlapping of p orbitals, perpendicular to internuclear axis

Question 16

Why do bond pairs have the least repulsion

Answer 16

Since the are under the influence of two nuclei, the contract and occupy a smaller space resulting in less repulsion

Question 17

State the geometry and angle of VSEPR

Answer 17

• 2 pair - linear - 180
• 3 pair - trigonal planar - 120
• 4 pair - tetrahedral - 109.5
• 5 pair - trigonal bipyramid - 120, 90
• 6 pair - octahedral - 90

Question 18

What is the bond angle of distorted pyramid

Answer 18

107

Question 19

What is the bond angle of bent or v shape

Answer 19

104.5

Question 20

What is hybridization

Answer 20

It is the intermixing of orbitals having similar energy to form orbitals with exactly the same energy with identical shapes and symmetrical orientations in space

Question 21

What is sigma molecular orbital

Answer 21

It the the molecular orbital formed from the head-on overlapping of s-s atomic orbitals or p-p atomic orbitals or s-p

Question 22

What is pi molecular orbital

Answer 22

A molecular orbital formed from sideways or lateral overlap of two p orbitals