Atoms, Elements and Compounds

You will be able to

• Determine the numbers of protons, neutrons and electrons in an atom or ion from its proton number, nucleon number and charge.
• State the electronic configuration of the first 20 elements and deduce the period and group from it.
• Calculate the relative atomic mass of an element from the masses and percentage abundances of its isotopes.

You will be able to

• Describe the formation of ions by electron loss or gain and draw dot-and-cross diagrams of ionic compounds.
• Deduce the formula of an ionic compound by balancing the charges on its ions.
• Explain the high melting points and electrical conductivity of ionic compounds in terms of the giant lattice of oppositely charged ions.

You will be able to

• Describe a covalent bond as a pair of electrons shared between two atoms, leading to noble-gas configurations.
• Draw dot-and-cross diagrams and displayed formulae of simple molecules with single, double and triple bonds.
• Explain why simple molecular substances have low melting and boiling points and do not conduct electricity.

You will be able to

• Describe the giant covalent structures of diamond, graphite and silicon(IV) oxide and relate them to their uses.
• Explain the melting points and electrical conductivity of giant ionic, giant covalent, metallic and simple molecular substances.
• Explain why metals are malleable but ionic solids are brittle.