Atoms. Elements & Compounds

C2.1 Elements, compounds and mixtures 1 Describe the differences between elements, compounds and mixtures C2.2 Atomic structure and the Periodic Table 1 Describe the structure of the atom as a central nucleus containing neutrons and protons, surrounded by electrons in shells 2 State the relative charges and relative masses of a proton, a neutron and an electron 3 Define proton number/atomic number as the number of protons in the nucleus of an atom 4 Define mass number/nucleon number as the total number of protons and neutrons in the nucleus of an atom 5 Determine the electronic configuration of elements with proton number 1 to 20, e.g. 2,8,3 6 State that: (a) Group VIII noble gases have a full outer shell (b) the number of outer-shell electrons is equal to the group number in Groups I to VIII (c) the number of occupied electron shells is equal to the period number C2.3 Isotopes 1 Define isotopes as different atoms of the same element that have the same number of protons but different numbers of neutrons 2 Interpret and use symbols for atoms, e.g. 126C , and ions, e.g. 3517Cl- 3 State that isotopes of the same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration C2.4 Ions and ionic bonds 1 Describe the formation of positive ions, known as cations, and negative ions, known as anions 2 State that an ionic bond is a strong electrostatic attraction between oppositely charged ions 3 Describe the formation of ionic bonds between elements from Group I and Group VII, including the use of dot-and-cross diagrams 4 Describe the properties of ionic compounds: (a) high melting points and boiling points (b) good electrical conductivity when aqueous or molten and poor when solid (c) generally soluble in water 5 Describe the formation of ionic bonds between ions of metallic and non-metallic elements, including the use of dot-and-cross diagrams 6 Explain in terms of structure and bonding the properties of ionic compounds: (a) high melting points and boiling points (b) good electrical conductivity when aqueous or molten and poor when solid 7 Describe the giant lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions, exemplified by sodium chloride C2.5 Simple molecules and covalent bonds 1 State that a covalent bond is formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations 2 Describe the formation of covalent bonds in simple molecules, including H2, Cl2, H2O, CH4, NH3 and HCl. Use dot-and cross diagrams to show electronic configurations in these molecules 3 Describe in terms of structure and bonding the properties of simple molecular compounds: (a) low melting points and boiling points (b) poor electrical conductivity 4 Describe the formation of covalent bonds in simple molecules, including CH3OH, C2H4, O2, CO2 and N2. Use dot-and-cross diagrams to show the electronic configurations in these molecules 5 Explain in terms of structure and bonding the properties of simple molecular compounds: (a) low melting points and boiling points in terms of weak intermolecular forces (specific types of intermolecular forces are not required) (b) poor electrical conductivity C2.6 Giant covalent structures 1 Describe the giant covalent structures of graphite and diamond 2 Relate the structures and bonding of graphite and diamond to their uses, limited to: (a) graphite as a lubricant and as an electrode (b) diamond in cutting tools C2.7 Metallic bonding 1 Describe metallic bonding as the electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons 2 Explain in terms of structure and bonding the properties of metals: (a) good electrical conductivity (b) malleability