Chem 2 - Bonding and Calculations - Covalent Bonding

Sometimes atoms like to make Covalent Bonds by Sharing electrons with other atoms.

They only share electrons in their Outer Shells. This way both atoms feel they have a full outer shell. (This gives them the structure of a noble gas)

Each covalent bond provides one extra electron for each atom. So a covalent bond is a shared pair of electrons. Each atom has to involved has to make enough covalent bonds to fill their outer shell. 

There are 7 important examples to learn:

- H2. Hydrogen goes around in pairs, as it only has one electron in its outer shell, and only needs one covalent bond.

- Cl2. Chlorine also goes round in pairs, as it only needs one electron to complete its outer shell.

- Methanes formula is CH4. Carbon has 4 outer electrons, which is half a full shell. So it forms 4 covalent bonds with 4 hydrogen atoms.

- Hydrogen Chloride (HCl). This is similar to H2 and Cl2, both elements need one electron to complete an outer shell, so one covalent bond is formed.

- Ammonia (NH3). Nitrogen has 5 outer electrons, and so forms 3 covalent bonds with 3 hydrogen atoms.

- Water (H2O). Oxygen has 6 outer electrons, and so forms 2 covalent bonds with 2 hydrogen atoms.

- O2. Oxygen also goes around in pairs, sharing 2 electrons with each other.