10. Forces between molecules - Hydrogen Bond

What is the hydrogen bond?

Extra strong dipole-dipole attraction between hydrogen atom bonded to small highly negative element

What molecules can hydrogen atom be bonded to (examples)? And how?

F, N + O, either within the same molecule (intramolecular) or on an adjacent molecule (intermolecular)

Why are the attractive forces stronger than in other intermolecular bonding?

Atoms are small and approach each other closely and dipole charges are relatively large

What happens because atoms are small, approach each other closely and dipole charges are relatively large?

Makes the attractive forces stronger than in other intermolecular bonding

What is a characteristic of the hydrogen bond?

It is directional

Draw a diagram to show bonding in water molecules?

Yes

Draw a diagram to show hydrogen bonding in hydrogen and fluorine

Yes

What occur in water due to hydrogen bonding?

Special properties meaning it can change its density depending on the state it is in

Draw diagram of ice

Yes

Describe hydrogen bonding in ice?

On reaching solid state, hydrogen bonds become stable, arranging water molecules far apart from each other

Describe hydrogen bonding in water?

In liquid state, water molecules closely held together by hydrogen bonds -> Causes ice to have less density making it float

What is the trend in boiling points of group IV hydrides?

BPT increases down group -> Increase Mr, Increase in electrons, Intermolecular forces (VDW) increase

What is the trend in boiling points in group VI hydrides?

BPT increases down group from H₂S -> Increase Mr, Increase in electrons, Intermolecular forces (VDW) increase

Why is H₂O an anomaly in this pattern?

BPT significantly higher -> Has both hydrogen and VDW so intermolecular forces of attraction are higher