XI: Chemical bonding

Question 1

Who gave the octet rule?

Answer 1

Kossel and Lewis

Question 2

Which bond is also known as electrovalent bond?

Answer 2

Ionic bond

Question 3

Is ionic bond directional?

Answer 3

No

Question 4

Is formation of gaseous cation by ionisation of gaseous atom endothermic or exothermic?

Answer 4

Endothermic

Question 5

First electron gain enthalpy for a gaseous atom is _____ (endothermic/exothermic)?

Answer 5

Exothermic

Question 6

Second electron gain enthalpy for a gaseous atom is _____ (endothermic/exothermic)?

Answer 6

Endothermic

Question 7

How does size of the ions in a lattice affect lattice enthalpy?

Answer 7

Smaller the size of ions, lesser is the internuclear distance and greater will be the interionic attraction.

Question 8

In sodium chloride lattice each sodium is surrounded by

Answer 8

six chlorine atom

Question 9

In sodium chloride lattice each chlorine is surrounded by

Answer 9

Six sodium atoms

Question 10

How many sodium and chlorine atoms are present in the unit cell of sodium chloride?

Answer 10

14 chlorine, 13 sodium

Question 11

WHich positions does chlorine occupy in sodium chloride unit cell?

Answer 11

In a unit cell Cl- ions occupy all the centres of six faces and eight corners, where as one sodium ion is present at the centre of body and twelve sodium ions are present at all the twelve edges.

Question 12

What type of interactions(forces) are present between ionic compounds and solvents like water?

Answer 12

Ionic dipole interactions

Question 13

The unshared electrons in chlorine molecules are all the electrons that do not participate in covalent bond formation. True/false.

Answer 13

False. The unshared electrons are lone pairs (only the valence electrons).

Question 14

What is covalency?

Answer 14

The number of electrons an element contributes for sharing while forming covalent bond.

Question 15

Do ionic compounds exist as individual molecules?

Answer 15

No. They exist in a lattice as individual ions.

Question 16

Do covalent compounds exist as individual molecules?

Answer 16

Yes

Question 17

WHich is slower- ionic reaction or molecular reaction?

Answer 17

Molecular reaction

Question 18

In a coordinate bond the donor atom may not have a complete octet. True/false?

Answer 18

False. Donor atom has a complete octet.

Question 19

Can a coordinate bond once formed be distinguished from a covalent bond?

Answer 19

No

Question 20

How is formal charge on a molecule calculated?

Answer 20

V − (1/2)S − L

V: valence electrons of atom
S: Number of shared electrons
L: Lone pairs

Question 21

Are covalent bonds directional?

Answer 21

Yes

Question 22

Which electron cloud occupies more space- lone pair or bond pair electron cloud?

Answer 22

Lone pair electron cloud

Question 23

When is a compound said to have regular geometry in accordance with VSEPR theory?

Answer 23

When all the electron pairs around central atom are bond pairs.

Question 24

When is a compound said to have distorted geometry in accordance with VSEPR theory?

Answer 24

When lone pairs are present on central atom in addition to bond pairs.

Question 25

Among molecules having irregular but similar geometry, how does bond angle vary with electronegativity of central atom?

Answer 25

Bond angle decreases with decreasing electronegativity of central atom.

Question 26

Among molecules having irregular but similar geometry, how does bond angle vary when central atom is kept same but electronegativity of surrounding atoms decreases?

Answer 26

Bond angle increases

Question 27

Does bond angle vary among molecules having regular but similar geometry with varying electronegativity of central or surrounding atoms?

Answer 27

No

Question 28

Is sigma bond formed by overlap of s and s orbitals stronger or sigma bond formed by overlap of p-p orbitals?

Answer 28

sigma bond formed by overlap of p-p orbitals

Question 29

Which bond determines the shape of molecule- sigma or pi?

Answer 29

Sigma bond

Question 30

In resonance structures, like charges can reside on adjacent atoms. True/false

Answer 30

False.

Question 31

A resonance hybrid can be represented by a Lewis structure. True/false?

Answer 31

False.

Question 32

What is the formula for bond order in resonance forms?

Answer 32

Total number of bonds between
two atoms in all resonating forms
___________________________

Total number of resonating forms

Question 33

An atomic orbital is polycentric and a molecular orbital is monocentric. True/false?

Answer 33

False.

An atomic orbital is monocentric and a molecular orbital is polycentric.

Question 34

Which is more pronounced according to molecular orbital theory- destabilising effect of antibonding orbitals or stabilising effect of bonding orbitals?

Answer 34

destabilising effect of antibonding orbitals

Question 35

Which type of molecular orbitals are called sigma orbitals?

Answer 35

Those which are cylindrically symmetrical about the intermolecular axis.

Question 36

If the number of electrons in bonding orbitals is equal to the number of electrons in antibonding orbitals, is the molecule stable?

Answer 36

No

Question 37

What type of interactions are hydrogen bonds?

Answer 37

Dipole dipole interaction

Question 38

Which has a smaller SiO bond order H2SiO or Cl2SiO?

Answer 38

Cl2SiO

due to back bonding

Question 39

Does methane have a net dipole moment?

Answer 39

Dipole moment of methane is zero