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

How high are ionically bonded substances’ bp and mp? Why?

Answer 2

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

Question 3

Do ionic compounds conduct electricity? Why?

Answer 3

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

Question 4

What is simple molecular covalent bonding?

Answer 4

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

Question 5

Are there any lone electrons in simple covalent bonding?

Answer 5

No- they are all involved in bonding

Question 6

Can simple molecular covalent molecules conduct electricity? why?

Answer 6

No- they are all involved in bonding and aren’t free to move

Question 7

Do simple molecular substances have a high/low mpt and bpt? why?

Answer 7

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 8

Describe macromolecular covalent bonding

Answer 8

Lattice of many atoms held together by strong covalent bonds

Question 9

Do substances with macromolecular covalent bonds

have high/low mpt and bpts? why?

Answer 9

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

Question 10

Do substances with macromolecular covalent bonds conduct electricity?

Answer 10

Most don’t as all electrons are used in bonding

Question 11

Describe the structure of diamond

Answer 11

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

Question 12

Describe the structure of graphite

Answer 12

Similar to diamond - macromolecular covalent - but each C atom is only bonded to3 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 13

Describe metallic bonding

Answer 13

Lattice of positive metal ions strongly attracted to a sea of delocalised electrons.

Layers can slide over each other - malleable

Question 14

Do metallic compounds have high/low bpt and mpts? why?

Answer 14

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

Question 15

Do metallic compounds conduct electricity? why?

Answer 15

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

Question 16

How does the strength of metallic bonds change

across the periodic table? Why?

Answer 16

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

Question 17

Define electronegativity

Answer 17

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

Question 18

What affects electronegativity? (3)

Answer 18

Nuclear charge
Atomic radius
Electron shielding

Question 19

What is the most electronegative element?

Answer 19

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

Question 20

How do you get a nonpolar bond?

Answer 20

Both bonding elements have the same electronegativities

Question 21

When do you get a polar bond?

Answer 21

Bonding atoms have different electronegativities

Question 22

What is the strongest type of inter-molecular force?

Answer 22

Hydrogen bonding

Question 23

What is the weakest type of inter-molecular force?

Answer 23

van der Waals

Question 24

Describe van der Waals’ forces of attraction.

Answer 24

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 25

Are Van der Waals forces stronger in smaller or larger molecules?

Answer 25

Larger as there are more electrons

Question 26

Describe permanent dipole-dipole attraction

Answer 26

Some molecules with polar bonds have permanent dipoles → forces of attraction between those dipoles and those of neighbouring molecules

Question 27

What conditions are needed for hydrogen bonding to

occur?

Answer 27

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 28

Why is ice less dense than liquid water?

Answer 28

In liquid water, hydrogen bonds constantly break and reform as molecules move about

In ice, the hydrogen bonds hold the molecules in fixed
positions; this makes them slightly further apart than in liquid water

Question 29

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

Answer 29

Formed when an electron deficient atom/ion accepts a lone pair of electrons from an atom/ion with a lone pair of electrons (not used in bonding)

Question 30

What does the shape of molecules depend on?

Answer 30

Number of electrons in the valence shell of the
central atom

Number of these electrons which are in bonded
or lone pairs

Question 31

What does the Electron Pair Repulsion Theory state?

Answer 31

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

Question 32

Which experience the most repulsion?

Answer 32

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