2. Atoms, elements and compounds
- Syllabus
- 0620–2026–2027
- Section
- 2
- Level
- —
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In this section
Topic 2.1
2.1 Elements, compounds and mixtures
Objectives in this topic
2.1.1—Differences between elements
- Describe differences between elements, compounds and mixtures
Topic 2.2
2.2 Atomic structure and the Periodic Table
Objectives in this topic
2.2.1—Structure of the atom as a central
- Describe structure of the atom as a central nucleus containing neutrons and protons surrounded by electrons in shells
2.2.2—Relative charges and relative masses
- State the relative charges and relative masses of a proton, a neutron and an electron
2.2.3—Proton number/atomic number as the
- Define proton number/atomic number as the number of protons in the nucleus of an atom
2.2.4—Mass number/nucleon number as the
- Define mass number/nucleon number as the total number of protons and neutrons in the nucleus of an atom
2.2.5—Electronic configuration of elements
- Determine the electronic configuration of elements and their ions with proton number 1 to 20, e.g. 2,8,3
2.2.6—Periodic table shell rules: (a) Group
- State periodic table shell rules: (a) Group VIII noble gases have full outer shells (b) outer-shell electrons equal group number in Groups I-VII (c) occupied shells equal period number
Topic 2.3
2.3 Isotopes
Objectives in this topic
2.3.1—Isotopes as different atoms of the
- Define isotopes as different atoms of the same element that have the same number of protons but different numbers of neutrons
2.3.2—Symbols for atoms and ions
- Interpret/use symbols for atoms and ions, e.g. 12C and 35Cl- notation with mass/nucleon and proton/atomic numbers
2.3.3—Isotopes of the same element have the
- State: isotopes of the same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration
2.3.4—Relative atomic mass of an element
- Calculate the relative atomic mass of an element from the relative masses and abundances of its isotopes
Topic 2.4
2.4 Ions and ionic bonds
Objectives in this topic
2.4.1—Formation of positive ions, known as
- Describe formation of positive ions, known as cations, and negative ions, known as anions
2.4.2—An ionic bond is a strong
- State: an ionic bond is a strong electrostatic attraction between oppositely charged ions
2.4.3—Formation of ionic bonds between
- Describe formation of ionic bonds between elements from Group I and Group VII, including the use of dot-and-cross diagrams
2.4.4—Properties of ionic compounds: (a)
- Describe properties of ionic compounds: (a) high melting points and boiling points (b) good electrical conductivity when aqueous or molten and poor when solid
2.4.5—Giant lattice structure of ionic
- Describe giant lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions
2.4.6—Formation of ionic bonds between ions
- Describe formation of ionic bonds between ions of metallic and non-metallic elements, including the use of dot-and-cross diagrams
2.4.7—Ionic compound properties from
- Explain ionic compound properties from structure/bonding: high melting/boiling points and electrical conductivity when molten or aqueous, but not solid
Topic 2.5
2.5 Simple molecules and covalent bonds
Objectives in this topic
2.5.1—Covalent bond is formed when a pair of
- State: a covalent bond is formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations
2.5.2—Formation of covalent bonds in simple
- Describe formation of covalent bonds in simple molecules, including H2, Cl2, H2O, CH4, NH3 and HCl. Use dot-and-cross diagrams to show the electronic configurations in these and similar molecules
2.5.3—Simple molecular compound properties
- Describe simple molecular compound properties from structure/bonding: low melting/boiling points and poor electrical conductivity
2.5.4—Formation of covalent bonds in simple
- Describe 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 and similar molecules
2.5.5—Simple molecular compound properties
- Explain simple molecular compound properties: low melting/boiling points due to weak intermolecular forces, and poor electrical conductivity
Topic 2.6
2.6 Giant covalent structures
Objectives in this topic
2.6.1—Giant covalent structures of graphite
- Describe giant covalent structures of graphite and diamond
2.6.2—Relate the structures and bonding of
- Relate the structures and bonding of graphite and diamond to their uses, (a) graphite as a lubricant and as an electrode (b) diamond in cutting tools
2.6.3—Giant covalent structure of
- Describe giant covalent structure of silicon(IV) oxide, SiO2
2.6.4—Similarity in properties between
- Describe similarity in properties between diamond and silicon(IV) oxide, related to their structures
Topic 2.7
2.7 Metallic bonding
Objectives in this topic
2.7.1—Metallic bonding as the electrostatic
- Describe metallic bonding as the electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons
2.7.2—Metallic properties from
- Explain metallic properties from structure/bonding: good electrical conductivity, malleability and ductility