IonicIonic bonding happens between metals and non-metals. The electrons in ionic bonding are given or taken. For example, Sodium + Chlorine --> Sodium Chloride. (Na + Cl --> NaCl ) Sodium only has one electron in its outer shell and Chlorine has 7 in its outer shell. All atoms want to be in a full other shell. Here, sodium will give one electron to chlorine. Both atoms now have a full outer shell. CovalentIn covalent bonds atoms share electrons. This happens between two non-metals. For example: Hydrogen + Oxygen --> Water ( 2H2 + O2 --> 2H2O ) An electron from the Oxygen and electron from Hydrogen are shared to ensure each atom has a full outer shell.