1.4 Bonding

Question 1

Define an ionic bond

Answer 1

Electrostatic attraction between oppositely charged ions

Question 2

Define a covalent bond

Answer 2

Shared electron pairs between two or more non-metal atoms

Question 3

Define a dative/coordinate bond

Answer 3

Shared pair of electrons that has been provided by one of the bonded atoms only

Question 4

Define electronegativity

Answer 4

The relative tendency of an atom to attract an electron pair in a covalent bonds

Question 5

Define electron density

Answer 5

The way a negative charge is distributed in a molecule

Question 6

What impacts electronegativity? What’s the trend across a period and down a group?

Answer 6

• nuclear charge, atomic radius and electron shielding
• decrease down a group and increase across a period

Question 7

What is a permanent dipole?

Answer 7

A small charge difference across a bond that results from a difference in the electronegativities of a bonded atom

Question 8

Van Dee Waals forces … when …. increase

Answer 8

• increase
• electrons

Question 9

What is a hydrogen bond?

Answer 9

Where the pair of electrons on an N, O or F (v electronegative) are attracted to the delta plus hydrogen in a neighbouring molecule

Question 10

What is the trend in boiling points in Group 0?

Answer 10

As you go down, the number of electrons increases and so BP increases as the strength of VdW increases so more energy is required to break the bonds

Question 11

What is the trend in boiling points in Group 4?

Answer 11

Increased BP due to increase electron number and therefore more energy required to break the stronger VdW

Question 12

What is the trend in boiling points in Group 5?

Answer 12

H bonds are stronger and so the BP is increased, but it initially drops at NH3 before gradually increasing

Question 13

What is the trend in boiling points in Group 7?

Answer 13

The H bonds are strongest in HF so BP decreases then increases

Question 14

Lone pairs ….

Answer 14

Repel more than bonding pairs

Question 15

2 Bond and 0 Lone

Answer 15

Linear, 180° angle

Question 16

3 Bond and 0 Lone

Answer 16

Trigonal planar, 120°

Question 17

4 Bond and 0 Lone

Answer 17

Tetrahedral, 109.5°

Question 18

5 Bond and 0 Lone

Answer 18

Trigonal bipyramid, 90° and 120°

Question 19

6 Bond and 0 Lone

Answer 19

Octahedral, 90°

Question 20

3 Bond and 1 Lone

Answer 20

Trigonal pyramid, 107°

Question 21

2 Bond and 2 Lone

Answer 21

V-shaped, 104.5°

Question 22

Describe 2 anamolous properties of water

Answer 22

• ice is lighter than water as H bonds hold H2O open in lattice and are longer between
• higher M/B point due to strength of H bonds needing to be broken

Question 23

Why does Silicon have a much higher BP than Phosphorus

Answer 23

• Si has strong forces between atoms and covalent bonds need breaking
• P has weak VdW which need less energy to break

Question 24

Define a polar covalent bond

Answer 24

A covalent bond where electrons are not shared equally

Question 25

Why do some bonds have dipoles?

Answer 25

Differences in electronegativities in the molecule

Question 26

Why does ammonia liquify better than ethane

Answer 26

Ammonia has H bonds whereas ethane has VdW. H stronger than VdW

Question 27

Why is NCl3 insoluble in water but NH3 very soluble?

Answer 27

NH3 forms H bonds with water molecules but NCl3 cannot do this

Question 28

Explain graph for Group 7 Bp

Answer 28

• more dipole-dipole as you descend the group
• HF has H bonds
• H bonds stronger than VdW and so BP higher as more energy needed to break

Question 29

Use electronegativity to explain why ammonium chloride is covalent and ammonium oxide is ionic

Answer 29

• difference in electronegativity is larger in aluminium oxide so it’s ionic
• difference smaller in aluminium chloride so it’s covalent

Question 30

Why is the bonding in silicon covalent?

Answer 30

• no electronegativity differences
• bonding electrons are shared equally