Chemical Bonding

Question 1

Reactivity of atoms

Answer 1

Atoms that have a FULL outer shell are unreactive. They are likely to remain as they are.
Atoms that do not naturally have a full valence shell will react and form chemical bonds with other atoms to achieve this – they will either:
gain electrons from other atoms,
give away electrons to other atoms,
share electrons with other atoms

Question 2

Forming ions

Answer 2

Elements with <4 valence electrons (usually metals) will react to lose electrons to other atoms to get a full outer shell, forming positive ions
Elements with >4 valence electrons (usually non-metals) will react to gain electrons from other atoms to get a full outer shell, forming negative ions