3.1.3 Bonding

Question 1

Name the 4 types of crystal structure.

Answer 1

• Simple molecular
• Ionic
• Metallic
• Macromolecular

Question 2

Give examples of macromolecular crystal structures.

Answer 2

• Silicon dioxide
• Diamond
• Graphite

Question 3

What is a covalent bond?

Answer 3

Shared pair of electrons between two non-metals

Question 4

What is a dative covalent bond?

Answer 4

When both electrons in a covalent bond are donated from one atom

Question 5

What is a metallic bond?

Answer 5

Strong electrostatic attraction between the positive metal ions and delocalised electrons

Question 6

Why can metallic compounds conduct electricity?

Answer 6

• Sea of delocalised electrons and positive metal ions.
• Delocalised electrons are free to flow and carry charge

Question 7

Why are metallic compounds malleable?

Answer 7

• Layers of positive metal ions able to slide over eachother
• Layers don’t repel because of delocalised electrons

Question 8

What are the factors that affect the strength of metallic bonds?

Answer 8

• Metal charge on ion (determines number of delocalised electrons per ion)
• Ionic radius on cation
  (nuclear charge + shielding)

Question 9

What is an ionic bond?

Answer 9

Strong electrostatic attraction between oppositely chagred ions.

Question 10

Why can ionic compounds conduct electricity when molten/liquid state and not as a solid?

Answer 10

• Ions are free to move and carry charge when molten/liquid
• When solid, ions not free to move and carry charge

Question 11

Why are ionic compounds hard and brittle?

Answer 11

• When layers slide over eachother the like charged ions repel eachother
• Layers repel and the structure breaks

Question 12

What does the strength of an ionic bond depend on?

Answer 12

• Ionic charge
• Ionic radius

Question 13

Shape and bond angle for the following molecules:
a) 2 bonding pairs
b) 3 bonding pairs
c) 2 bonding pairs + 1 lone pair

Answer 13

a) Linear, 180°
b) Trigonal planar, 120°
c) V-shaped, 118°

Question 14

Shape and bond angle for the following 4 electron pair molecules:
a) 4 bonding pairs
b) 4 bonding pairs + 1 lone pair
c) 4 bonding pairs + 2 lone pair

Answer 14

a) Tetrehedral, 109°
b) Trigonal pyramidal 107°
c) V-shaped, 105°

Question 15

Shape and bond angle for the following 5 electron pair molecules:
a) 5 bonding pairs
b) 4 bonding pairs + 1 lone pair
c) 3 bonding pairs + 2 lone pair

Answer 15

a) Trigonal bipyramid, 90° and 120°
b) no name, 119° and 89°
c) T-shape, 89°

Question 16

Shape and bond angle for the following molecules:
a) 6 bonding pairs
b) 5 bonding pairs + 1 lone pair
c) 4 bonding pairs + 2 lone pair

Answer 16

a) Octhedral, 90°
b) Distorted square pyramid, 89°
c) Square planar, 90°

Question 17

In terms of electron pairs, explain why the bond angles in a NH4+ ion are all 109°?

Answer 17

• 4 bonding pairs of electron
• All equally repel eachother as far apart as possible
• Creating a tetrehdral shape with 109° bond angles

Question 18

What are the 3 types of IMFs?

Answer 18

1. Hydgrogen bonds
2. Permanent dipole-dipole interactions
3. Van der Waals’ forces

Question 19

What controls the strength of Van der Waals’?

Answer 19

Nuclear charge and number of electrons

Question 20

What IMF is present in a molecule of SiF4? Why are no other IMFs present?

Answer 20

• Van der Waals’
• No H-bonds due to lack of electronegativty difference
• No permant dipole-dipole interactions as molecule is symetrical, dipoles cancel

Question 21

Give the meaning of the term electronegativity?

Answer 21

The ability of an atom to attract a bonding pair of electrons towards itself in a covalent bond

Question 22

Why does electronegativity increase from left to right across a period?

Answer 22

• Similar shielding
• Increased nuclear charge
• Smaller atomic radius

Question 23

Why is an O-H bond in a molecule polar?

Answer 23

• Oxygen has high electronegativity
• Hydrogen has lower
• Oxygen atom attracts electron density

Question 24

Explain how the strongest type of IMF in liquid HF arises.

Answer 24

• Large difference in electronegativity between hydrogen and fluorine, polar H-F bond
• Dipole: partially positive hydrogen, partially negative fluorine
• Partially positive hydrogen attracts to lone pair of electrons on fluroine

Question 25

Why does boiling point of hydrogen halides increase from HCl to HI?

Answer 25

- Nuclear charge increases, more electrons present as you go down group - Strong Van der Waals' - Requires more energy to overcome

Question 26

Why is the boiling point of HF the highest for all the hydrogen halides?

Answer 26

- Only one with hydrgoen bonds - Stronger IMF that requires more energy to overcome