Topic 2 electronegativity and forces

Question 1

Electronegativity

Answer 1

Ability for an atom to attract electrons towards itself in a covalent bond

Question 2

How can covalent bonds become polar

Answer 2

If the atoms attached to it have a difference in electronegativity

Question 3

Bigger difference in electronegativity =

Answer 3

more polar the bond will be

Question 4

London forces (instantaneous dipole - induced dipole)

Answer 4

Occurs as electrons in a molecule or tom can move from one end to another, creating a temporary dipole

Question 5

Longer straight chain hydrocarbons would have a higher boiling point…

Answer 5

As they have more london forces that require more energy to overcome.

Question 6

Branched hydrocarbons have lower boiling points as…

Answer 6

they can’t pack together as close, reducing surface contact, which lowers their boiling point.

Question 7

Permanent dipole-dipole

Answer 7

Weak electrostatic forces that exist between molecules with a polarity. (stronger than london forces)

Question 8

Hydrogen bonding

Answer 8

When hydrogen bonding occurs when hydrogen on one molecule forms a bond with the lone pair on Nitrogen, Oxygen or fluorine (3 most electronegative elements)

Question 9

Why is ice less dense than water

Answer 9

Ice forms a regular structure held by hydrogen bonds. These molecules are held further apart.

Question 10

Why does HF have a higher boiling point that HCl

Answer 10

HF contains hydrogen bonds, whereas HCL contains permanent dipole-dipole forces which are weaker than hydrogen bonds

Question 11

Explain the boiling point trend of HCl<HBr<HI

Answer 11

Increasing mass of molecule, hence bigger electron cloud and thus more london forces.