Covalent Bonding In a covalent bond electrons are shared between two atoms. Hydrogen is diatomic, energy is released when bonds are formed making H2 more stable. Molecules with a full outer shell become noble gas forms, very unreactive.
Ionic Bonding Electrically charged ions are called Ions
Metallic Bonding In the example of Na, the outer electron of each atom becomes ‘delocalised’ and free to move. This forms a ‘sea of delocalised electrons’ that can carry a charge. The difference in charge between the positive ions and the sea of delocalised electrons holds the metal together.
Sodium is a relatively weak metal, as there is only one electron per ion, so the difference in charge is less, and therefore the force of attraction. However in a metal like iron the difference in charge will be much greater as there are more electrons in the outer shell.
Giant Metallic Structures ● Strong, high BP, high MP
● Metals are elastic and will return to their original shape
● Malleable/Ductile shifting rows of ions will result in no repelling charges because of the sea of electrons
● Metals can be alloyed
● The different sized particles disrupt metallic bonding, usually making the alloy stronger and harder.
Intermolecular Forces Forces of attraction between molecules, Van de Waals forces. The side of a molecule is either slightly negative or positive and these subtle differences in charge hold the molecules together.
Melting or boiling of substances doesn’t break covalent bonds, but the intermolecular forces. Structure Giant Ionic Giant Ionic compounds consist of huge lattices of tightly packed positive and negative ions. ● High melting and boiling points
● Ionic compounds tend to be crystalline
● Brittle, any distortion of a crystalline brings ions with the same charge alongside each other like