3.1.3 Bonding

Question 1

What is ionic bonding?

Answer 1

Strong electrostatic forces of attraction between oppositely charged ions held in a lattice

Question 2

Give an example of an ionically bonded substance

Answer 2

NaCl (sodium chloride - salt)

Question 3

How high are ionically bonded substances’ boiling points and melting points? Why?

Answer 3

High
- takes lots of energy to break strong electrostatic forces of attraction between oppositely charged ions

Question 4

Do ionic compounds conduct electricity? Why?

Answer 4

Yes, when molten/in solution as the ions are free to move and carry charge (don’t when solid)

Question 5

What is simple molecular covalent bonding?

Answer 5

Strong covalent bonds between atoms, weak van der Waals forces of attraction between molecules

Question 6

Are there any lone electrons in simple covalent bonding?

Answer 6

No - all involved in bonding

Question 7

Can simple molecular covalent molecules conduct electricity? Why?

Answer 7

No - all electrons used in bonding and aren’t free to move.

Question 8

Do simple molecular substances have a high/low melting point and boiling point? Why?

Answer 8

Low - weak van der Waals forces of attraction between molecules that don’t take much energy to overcome (these are overcome rather than covalent bonds)

Question 9

Describe macromolecular covalent bonding.

Answer 9

Lattice of many atoms held together by strong covalent bonds.

Question 10

Do substances with macromolecular covalent bonds have high/low melting point and boiling points? Why?

Answer 10

High, as it takes a lot of energy to overcome many strong covalent bonds

Question 11

Do substances with macromolecular covalent bonds conduct electricity?

Answer 11

Most don’t as all electrons are used in bonding.

Question 12

Describe structure of diamond.

Answer 12

3D tetrahedral structure of C atoms, with each C atom bonded to four others.

Question 13

Describe the structure of graphite.

Answer 13

• Similar to diamond - macromolecular covalent - but each carbon atom is only bonded to 3 others, so it is in layers
• Weak van der Waals forces of attraction between layers mean they can slide over each other -> soft, slippery
• one electron from each carbon is delocalised and can carry charge -> conducts electricity

Question 14

Describe metallic bonding.

Answer 14

Lattice of positive metal ions strongly attracted to a sea of delocalised electrons.
Layers can slide over each other - malleable

Question 15

Do metallic compounds have high/low boiling points and melting points? Why?

Answer 15

High as strong forces of attraction between positive metal ions and negatively changed sea of delocalised electrons.

Question 16

Do metallic compounds conduct electricity? Why?

Answer 16

Yes as delocalised electrons can move throughout the metal to carry charge.

Question 17

How does the strength of metallic bonds change across the periodic table? Why?

Answer 17

Increases -> higher melting and boiling points, stronger
- Higher charge on metal ions
- More delocalised electrons per ion
- Stronger force of attraction between them

Question 18

Define electronegativity.

Answer 18

The ability of an atom to attract the pair of electrons (the electron density) in a covalent bond.

Question 19

What affects electronegativity? (3)

Answer 19

• nuclear charge
• atomic radius
• electron shielding

Question 20

What is the most electronegative element?

Answer 20

Fluorine (4.0 on Pauling’s scale) -> largest nuclear charge for its electron shielding, small atomic radius

Question 21

How do you get a non-polar bond?

Answer 21

Both bonding elements have the same electronegativities.

Question 22

When do you get a polar bond?

Answer 22

Bonding atoms have different electronegativities.

Question 23

What is the strongest type of inter-molecular force?

Answer 23

Hydrogen bonding

Question 24

What is the weakest type of inter-molecular force?

Answer 24

van der Waals forces

Question 25

Describe van der Waals' forces of attraction.

Answer 25

Temporary dipoles are created by the random movement of electrons -> induces dipole in neighbouring molecule -> temporary induced dipole-dipole attraction aka van der Waals forces of attraction.

Question 26

Are van der Waals forces greater in smaller or larger molecules?

Answer 26

Larger - more electrons

Question 27

Describe permanent dipole-dipole attraction.

Answer 27

Some molecules with polar bonds have permanent dipoles -> forces of attraction between those dipoles and those of neighbouring molecules.

Question 28

What conditions are needed for hydrogen bonding to occur?

Answer 28

- O-H, N-H or F-H bond, lone pair of electrons on O, F, N - Because O, N and F are highly electronegative, H nucleus is left exposed - Strong force of attraction between H nucleus and lone pair of electrons on O, N, F

Question 29

Draw a diagram of hydrogen bonding.

Answer 29

Question 30

Why is ice less dense than liquid water?

Answer 30

In liquid water, hydrogen bonds constantly break and reform as molecules move about. In ice, the hydrogen bonds hold the molecules in fixed position making them slightly further apart than in liquid water.

Question 31

What is a dative/co-ordinate covalent bond? When is it formed?

Answer 31

Formed when an electron deficient atom/ion accepts a lone pair of electrons from an atom/ion with a lone pair of electrons

Question 32

Draw the formation of a dative covalent bond in ammonia.

Answer 32

Question 33

What does the shape of molecules depend on?

Answer 33

Number of electrons in the valence shell of the central atom.

Question 34

What does the Electron Pair Repulsion Theory state?

Answer 34

That electron pairs will take up positions as far away from each other as possible, to minimise the repulsive forces between them.

Question 35

Which experience the most repulsion? Lone pair-lone pair Lone pair-bonded pair Bonded pair-bonded pair

Answer 35

LP-LP repulsion strongest LP-BP repulsion middle BP-BP repulsion weakest

Question 36

What is the shape and bond angle in a shape with 2 bonded pairs and 0 lone pairs?

Answer 36

Linear 180°

Question 37

What is the shape and the bond angle in a shape with 3 bonding pairs and 0 lone pairs?

Answer 37

Trigonal planar 120°

Question 38

What is the shape and bond angle in a shape with 4 bonded pairs and 0 lone pairs?

Answer 38

Tetrahedral 109.5°

Question 39

What is the shape and bond angle in a shape with 5 bonded pairs and 0 lone pairs?

Answer 39

Trigonal bipyramid 90° and 120°

Question 40

What is the shape and bond angle in a shape with 6 bonded pairs and 0 lone pairs?

Answer 40

Octahedral 90°