C2.5 Covalent Bonding

formed when 2 non-meta; atoms share pairs of electrons. Covalent bonds are strong because the shared electrons are attracted to the nucleus of both atoms. Covalently bonded substances can be: small molecules (E.g. water), Large molecules (E.g. polymers such as silk), Giant covalent structures (E.g. diamond)

Each hydrogen atom needs to get 1 extra electron to get a full outer electron shell. Each hydrogen atom shares 1 electron with the other, leaving 1 pair of electrons in the shared space between the atoms. This is a single covalent bond

Dot and cross with shells: dots represent the outer shell electrons of atoms of 1 element. Crosses represent the outer shell electrons of atoms of the other element.

Ball and stick: balls represent atoms. Sticks represent bonds between the atoms.

Lines: the atomic symbol represents the atom. Lines between the atoms represent a covalent bond

intramolecular forces are forces within molecules. Small covalent molecules are held together by strong intramolecular forces called covalent bonds. Lots of small covalent molecules can be held together by intermolecular forces. But these intermolecular forces are weak and easy to break. This means small covalent molecules have low melting and boiling points ( often liquids or gases at room temp)

Intra: strong covalent bonds found within small molecules

Inter: weak forces found between small molecules

small molecules don’t contain delocalised electrons because of this they cannot conduct electricity.

Giant covalent structures: no specific formula - the structure can be any size. very high melting points - high temp and high energy are required to break the structures covalent bonds. 1 large molecule - they exist as 1 large structure or molecule. there are no intermolecular forces because there is only 1 molecule.

Polymers are large, chain-like molecules that can extend for thousands of atoms

Polymers are held together by: strong covalent bonds between atoms in molecules. weak intermolecular forces between molecules