List two things (number them 1 and 2) that are special about hydrogen allowing it to form hydrogen bonds when bound to oxygen: 1 ... 2 ... List two things (number them 3 and 4) that are special about oxygen allowing it to form hydrogen bonds when bound to hydrogen: 3 ... 4 ...

Hydrogen

1. has one electron in the outermost shell

2. It is less electronegative

Oxygen

3. It requires two electrons to complete its outer shell

4. It is more electronegative

Explanation:

Each hyrogen of two will share its electron with oxygen. Oxygen requires two electrons to complete its outer shell so it will share with two hydrogen. Covalent bonds formed will be polar as oxygen will attract electrons towards it due to high electronegativity. This happens in water molecule

1. Presence of one valence electron in the outermost shell.

2. Less electronegative than Oxygen.

3. Six valence electrons its outer shell. So it needs to 2 electrons to get stable octet.

4. It is highly electronegative.

Explanation:

Hydrogen with the electronic configuration of 1s^1 needs 1 electron in its outer shell to be stable while oxygen with the electronic configuration of 1s^2 2s^2 2p^4 needs 2 electrons to complete octet state.

2 hydrogen atoms therefore bond covalently (sharing of electrons) with 1 Oxygen atom via hydrogen bond to form a water molecule.

This covalent hydrogen bond formed is polar as oxygen will attract electrons towards it due to high electronegativity.