Chemistry
Master Notes

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
Positive
= cation
Negative
= anion

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