Question: What’s the difference between a covalent bond and a non covalent bond?

Michael Nolan answered on 20 Jan 2021:

I’m not sure how much chemistry you have done, so here goes
1. When we build molecules from atoms, at least two atoms have to come close to each other
2. The two atoms have to either give away/receive or share electrons (all chemistry is driven by what electrons do)
3. If we think of a sodium atom and a chlorine atom (Na and Cl –> NaCl, table salt), then we know sodium has one electron that it likes to give away. Conversely chlorine would like to receive one more electron. In both cases their shells of electrons are filled and everyone is happy. The sodium is now positively charged (it gave away one electron) and the chlorine is negatively charged and this way of bonding is called “ionic” bonding as it involves two oppositely charged ions coming together.
4. For covalent bonding, we do not have this giving away and receiving of electrons. Instead the atoms, for example a carbon and hydrogen come together to “share” a pair of electrons (one electron from each atom). Given a carbon atom has 4 electrons (but wants 8) and hydrogen has one electron and wants to have two we can have one carbon and four hydrogen atoms making CH4, where there are four of these shared electron pairs. This covalent bonding makes up your typical organic molecules such as methane, acetic acid, ethanol etc. Ionic bonding tends to make solid materials.
5. There is also metallic bonding in copper or gold, which conduct electricity
6. Finally, we have interactions that involve no sharing or giving away electrons and these are called “non-bonded”. This is seen in water and these interactions contribute to it being liquid at room temperature