Chemical Bonding: 19 MCQs with answers

Sodium and chlorine

Ionic bonds form between a metal (low electronegativity) and a non-metal (high electronegativity). Sodium (metal) and chlorine (non-metal) have a large electronegativity difference, leading to electron transfer and ionic bond formation.

8

The octet rule states that atoms are most stable when they have eight electrons in their outermost shell, resembling the electron configuration of a noble gas.

σ bond

A sigma (σ) bond is formed by the head-on overlap of atomic orbitals along the internuclear axis, while a pi (π) bond involves sidewise overlap.

H2O

H2O has two bonding pairs and two lone pairs on the central oxygen, resulting in a bent shape with a bond angle of about 104.5°.

True

Sigma bonds involve greater orbital overlap along the internuclear axis, making them stronger than pi bonds, which have sidewise overlap.

CO2

CO2 has two bonding pairs and no lone pairs on the central carbon atom, leading to a linear geometry with a bond angle of 180°.

sp2

In BF3, boron has three bonding pairs and no lone pairs, requiring three equivalent orbitals, which corresponds to sp2 hybridization and a trigonal planar shape.

O-H

Polarity depends on electronegativity difference. Fluorine is the most electronegative element, so the F-H bond has the largest electronegativity difference and is the most polar among the given options.

2

O2 has a bond order of 2, calculated as (number of bonding electrons - number of antibonding electrons)/2 = (10-6)/2 = 2.

BF3

BF3 is trigonal planar and symmetrical, so the individual bond dipoles cancel out, resulting in a net dipole moment of zero.

NH3

NH3 has three bonding pairs and one lone pair on nitrogen, leading to a trigonal pyramidal shape due to lone pair repulsion.

104.5°

H2O has two lone pairs on oxygen, which compress the bond angle from the ideal tetrahedral angle (109.5°) to about 104.5°.

BeCl2

BeCl2 has two bonding pairs and no lone pairs on beryllium, leading to a linear geometry with a bond angle of 180°.

H2O

H2O is bent and has polar O-H bonds that do not cancel out, resulting in a net dipole moment. CO2, BF3, and CH4 are symmetrical and have zero dipole moments.

False

According to VSEPR theory, the shape is determined by the total number of electron pairs (bonding and lone pairs) around the central atom, as lone pairs also influence geometry.

BF3

BF3 has only six electrons around boron, making it electron-deficient and an exception to the octet rule.

Resonance structures differ only in the distribution of electrons.

Resonance structures represent the same molecule with the same arrangement of atoms but different distributions of electrons. The actual molecule is a hybrid of all resonance structures.

PCl5

PCl5 has five bonding pairs around phosphorus, requiring sp3d hybridization to accommodate five electron pairs in a trigonal bipyramidal arrangement.

C-C > C=C > C≡C

Bond length decreases as bond order increases. A triple bond is shorter than a double bond, which is shorter than a single bond.