1.4- Bonding

Question 1

(a)

Ionic bonding

Answer 1

Ionic bonding occurs when a metal and a non-metal react. The metal loses electrons to form a positively charged cation (+), while the non-metal gains electrons to form a negatively charged anion (-). These oppositely charged ions are held together by strong electrostatic forces of attraction.

Question 2

(b)

Covalent bonding

Answer 2

Covalent bonding occurs when non-metals bond by sharing electrons in their outer shells. Each atom donates one electron to form a bond pair with opposite spins. The bond is held together by the electrostatic attraction between the positive nuclei of the bonded atoms and the shared electrons.

Question 3

(b)

Coordinate bonding

Answer 3

The same as a covalent bond but both electrons forming the bond pair come from the same atom.

Question 4

(c)

intermediate character of many bonds between purely ionic and purely covalent

Answer 4

Most compounds are not purely ionic or covalent but have bonds with both characteristics, called polar bonds. The degree of ionic or covalent character depends on the electronegativity difference between atoms—the greater the difference, the more ionic the bond.

Question 5

(d)

Electronegativity

Answer 5

Electronegativity measures how strongly an atom attracts electrons in a covalent bond. The higher the electronegativity, the greater the atom’s ability to attract bonding electrons.

Question 6

(d)

Bond polarity

Answer 6

In a covalent bond, electrons are usually shared unevenly due to differences in electronegativity. The more electronegative atom pulls the bonding electrons closer, gaining a slight negative charge (δ⁻), while the other becomes slightly positive (δ⁺). This creates a polar bond. If the atoms have equal electronegativities, the electrons are shared equally, making the bond non-polar.

Question 7

(d)

Bond polarity (2)

Answer 7

In general, bonds where the electronegativity difference between the two atoms is less than about 0.4 will be non-polar covalent bonds. If the electronegativity difference is between 0.4 and about 1.9 then they will be polar covalent bonds. If the difference is about 2.0 or more, they will be ionic.

Question 8

(e)

forces between molecules being much weaker than covalent (and ionic) bonds

Question 9

(f)

Dipole-dipole forces

Answer 9

Polar molecules have dipoles, with one end slightly positive (δ⁺) and the other slightly negative (δ⁻) due to differences in electronegativity. If dipoles align so that the negative region of one molecule is near the positive region of another, an attraction forms between them.

Question 10

(f)

Induced dipole-induced dipole forces

Answer 10

Electrons are constantly moving, creating temporary dipoles as their distribution becomes uneven. These temporary dipoles induce dipoles in neighboring molecules, leading to attraction. The more electrons a molecule has, the stronger these induced dipole-induced dipole forces become, increasing intermolecular attraction. (van der Waals)

Question 11

(g)

Hydrogen bonding

Answer 11

Hydrogen bonding occurs in molecules where hydrogen is bonded to fluorine, oxygen, or nitrogen. These atoms are highly electronegative, creating a δ⁺ charge on hydrogen with high charge density. This δ⁺ hydrogen attracts a lone pair on a highly electronegative atom in another molecule, forming a hydrogen bond. The hydrogen is covalently bonded to one atom and hydrogen-bonded to another.

Question 12

(g)

Effects of hydrogen bonding

Answer 12

Hydrogen bonding increases boiling points because more energy is needed to overcome these stronger forces compared to van der Waals forces.

It also increases solubility, as substances that can form hydrogen bonds with water can dissolve by replacing existing hydrogen bonds between water molecules.

Question 13

(h)

VSEPR principle and its use in predicting the shapes of simple molecules and ions

Answer 13

Molecular shape is determined by the repulsion between electron pairs around the central atom. Lone pairs repel more strongly than bonding pairs, following the order: lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair. This repulsion affects bond angles and molecular geometry.

Question 14

(i)

Name the shape of BeCl2. What is the bond angle?

Answer 14

Linear
Angle= 180 °

Question 15

(i)

Name the shape of BCl3. What is the bond angle?

Answer 15

Trigonal planar
Angle= 120°

Question 16

(i)

Name the shape of CH4. What is the bond angle?

Answer 16

Tetrahedral
Angle = 109.5°

Question 17

(i)

Name the shape of NH3. What is the bond angle?

Answer 17

Trigonal pyramidal
Bond angle = 107°

Question 18

(i)

Name the shape of NH4+ . What is the bond angle?

Answer 18

Tetrahedral
Bond angle = 109.5

Question 19

(i)

Name the shape of H2O. What is the bond angle?

Answer 19

Bent
Bond angle = 104.5°

Question 20

(i)

Name the shape of SF6. What is the bond angle?

Answer 20

Octahedral
Bond angle = 90°