Covalent Bonding

What is a covalent bond?

This is a shared pair of electrons between two non-metal atoms. If each atom shares 2 electrons, it is called a double covalent bond. E.g. in oxygen, as each oxygen atom has 6 outer shell electrons it shares 2 electrons to have 8 as a full outer shell, hence oxygen is diatomic. O₂

Each of the positively charged nuclei is attracted to the same negatively charged pair of electrons, which is why covalent bonds are so strong.

Why does hydrogen form molecules? 

Whenever a bond is formed (of whatever kind), energy is released, and that makes the things involved more stable than they were before. The more bonds an atom can form, the more energy is released and the more stable the system becomes.

In the case of hydrogen, each hydrogen atom has only one electron to share, so it can only form one covalent bond. The H₂ molecule is still much more stable than two separate hydrogen atoms.

The significance of noble gas structures in covalent bonding

The formation of covalent bonds producing noble gas structures is quite common. When atoms bond covalently, they often produce outer electronic structures the same as noble gases-full outer shell. This is so they become stable and unreactive. The more electrons shared, the more covalent bonds there are, the more stable the molecule is.