1:40 draw dot-and-cross diagrams to show the formation of ionic compounds by electron transfer, limited to combinations of elements from Groups 1, 2, 3 and 5, 6, 7 only outer electrons need be shown
Sodium chloride, NaCl
Calcium oxide, CaO
Ionic bonding: a strong electrostatic attraction between oppositely charged ions.
A covalent bond is formed between two non-metal atoms by sharing a pair of electrons in order to fill the outer shell.
Covalent bonding: a strong attraction between a shared pair of electrons and two nuclei.
1:46 understand how to use dot-and-cross diagrams to represent covalent bonds in: diatomic molecules, including hydrogen, oxygen, nitrogen, halogens and hydrogen halides, inorganic molecules including water, ammonia and carbon dioxide, organic molecules containing up to two carbon atoms, including methane, ethane, ethene and those containing halogen atoms
1:49 explain why substances with giant covalent structures are solids with high melting and boiling points
Diamond has a high melting point because it is a giant covalent structure with many strong covalent bonds that require a lot of energy to break.
1:56 (Triple only) understand why ionic compounds conduct electricity only when molten or in aqueous solution
Ionic compounds only conduct electricity only when molten or in solution.
When solid the ions are not free to move.
When molten or in solution the ions are free to move.