Chemical bonds: strong electrostatic forces that hold particles together

1. A chemical bond is a strong electrostatic force of attraction that holds particles together in a substance.
2. An electrostatic force is simply the attraction between opposite electrical charges, one positive and one negative.
3. When atoms bond, only their outer-shell electrons are rearranged.
   1. These electrons can be transferred, shared in pairs, or shared as delocalised electrons.
4. There are three types of strong chemical bond: ionic, covalent and metallic.
   1. Each type creates regions of positive and negative charge that attract one another.

Choosing the bond type: the elements present tell you how the electrons behave

1. Ionic bonding forms when a metal combines with a non-metal.
   1. Electrons are transferred from the metal atoms to the non-metal atoms.
   2. The metal atoms become positive ions and the non-metal atoms become negative ions, such as ${Na}^{+}$ and ${Cl}^{-}$.
   3. Strong electrostatic forces between the oppositely charged ions are the ionic bonds.
2. Covalent bonding forms in most non-metallic elements and in compounds made only from non-metals.
   1. The non-metal atoms share one or more pairs of electrons.
   2. Each shared pair of negative electrons is attracted to the positive nuclei of both bonded atoms, which is what holds them together.
3. Metallic bonding occurs in metallic elements and in alloys.
   1. Each metal atom releases its outer electrons into a shared sea of delocalised electrons that are free to move.
   2. Strong electrostatic attraction between the positive metal ions and the negative delocalised electrons holds the structure together.

Explaining a bond: always name the positive part and the negative part

1. For ionic bonding, say that positive ions and negative ions attract because opposite charges attract.
   1. Add that electrons are transferred from the metal atoms to the non-metal atoms.
2. For covalent bonding, say that a negative shared pair of electrons is attracted to the positive nuclei of both atoms.
   1. Add that the atoms share one or more pairs of electrons.
3. For metallic bonding, say that positive metal ions are attracted to negative delocalised electrons.
   1. Add that the delocalised electrons are shared throughout the whole metal or alloy.

Classifying a substance: identify the elements, then explain the electrons

1. First decide whether each element present is a metal or a non-metal.
2. A metal combined with a non-metal usually gives ionic bonding.
3. Non-metals bonded to non-metals usually give covalent bonding.
4. A metallic element or an alloy has metallic bonding.
5. In every explanation, name what happens to the electrons and identify the opposite charges that attract.