Shapes of molecules - lone pair edition

Question 1

What is the effect of lone pairs on the shape of moleucles

Answer 1

effects the shape of the molecule always watch out for lone paurs on dot-and-cross diagrams e.g water and ammonia the bond angles are reduced by 2 degrees per lone pair

Question 2

What is unusual about ammonia?

Answer 2

ammonia has four pars of electrons

one of the groups is a lone pair

the molecule has a shaped based on a tetrahedron due to its lone pairs

but there are only 3 arms therefore the shape is that of a triangular pyramid

angles are approxnmitely 107

Question 3

What is unusual about water?

Answer 3

angles become a v shape because of the 2 pairs of lone electrons

bond angles are reduced to 104.5

lone-pair lone-pair repel more than lone-pair bonding-pair

Question 4

What is unusual about chlorine tetrafluoride ion?

Answer 4

four bonding pairs and 2 lone pairs charge of the ion is negative one because the lone pairs contain an electron that has been donated leaves a square planar because of the lone pair repulsion

Question 5

What is an example of and the bonding angles in a bent molecule?

Answer 5

water consists of two lone pairs and two bonding pairs bond angle of 104

Question 6

What is an example of and the bonding angles in a pyramidal bond angle?

Answer 6

bond angle of 107 threee bonding pairs and one lone pair

Question 7

Name this:

Answer 7

pyramidal

Question 8

Name this:

Answer 8

pyramidal

Question 9

Name this:

Answer 9

bent

Question 10

Name this:

Answer 10

hopper

Question 11

Explain why the bond angle in an amide ion (NH2^-) is smaller than that in an ammonia molecule.

Answer 11

• amide ion has more lone pairs than ammonia
• lone pairs of electrons repel more than bonding pairs

must be a comparison