Structure 3.1 The periodic table: Classification of elements
Structure 3.1.1 and 3.1.2
Understandings:
  • The periodic table consists of periods, groups and blocks (3.1.1).
  • The period number shows the outer energy level that is occupied by electrons. Elements in a group have a common number of valence electrons (3.1.2).
Learning outcomes:
  • Identify the positions of metals, metalloids and non-metals in the periodic table (3.1.1).
  • Deduce the electron configuration of an atom up to Z = 36 from the element’s position in the periodic table and vice versa (3.1.2).
Additional notes:
  • The four blocks associated with the sublevels s, p, d, f should be recognized.
  • A copy of the periodic table is available in the data booklet.​
  • Groups are numbered from 1 to 18.
  • The classifications “alkali metals”, “halogens”, “transition elements” and “noble gases” should be known.
Linking question(s):
  • Structure 1.2 How has the organization of elements in the periodic table facilitated the discovery of new elements?
This video covers groups, periods and the names of the groups. 
This video covers the blocks of the periodic table and electron configurations. 
This video covers the properties of metals and non-metals. 

This video covers the metalloids. 
Structure 3.1.3
Understandings:
  • Periodicity refers to trends in properties of elements across a period and down a group.
Learning outcomes:
  • Explain the periodicity of atomic radius, ionic radius, ionization energy, electron affinity and electronegativity.​
This video covers electron shielding and effective nuclear charge.
This video covers atomic radius.
This video covers ionic radius.
This video covers ionisation energy.
This video covers electron affinity.
This video covers electronegativity.
Structure 3.1.4
Understandings:
  • Trends in properties of elements down a group include the increasing metallic character of group 1 elements and decreasing non-metallic character of group 17 elements.
Learning outcomes:
  • Describe and explain the reactions of group 1 metals with water, and of group 17 elements with halide ions.​
This video covers metallic character.
This video covers the group 1 metals. 
This video covers the group 17 elements. 
Structure 3.1.5
Understandings:
  • Metallic and non-metallic properties show a continuum. This includes the trend from basic metal oxides through amphoteric to acidic non-metal oxides.
Learning outcomes:
  • Deduce equations for the reactions with water of the oxides of group 1 and group 2 metals, carbon and sulfur.
Additional notes:
  • Include acid rain caused by gaseous non-metal oxides, and ocean acidification caused by increasing CO2 levels.
Linking questions:
  • Structure 2.1, 2.2 How do differences in bonding explain the differences in the properties of metal and non-metal oxides?
This video covers the acid-base properties of the period 3 oxides. 
This video covers acid deposition (acid rain). 
This video covers ocean acidification. 
Structure 3.1.6
Understandings:
  • The oxidation state is a number assigned to an atom to show the number of electrons transferred in forming a bond. It is the charge that atom would have if the compound were composed of ions.
Learning outcomes:
  • Deduce the oxidation states of an atom in an ion or a compound.
  • Explain why the oxidation state of an element is zero.
Additional notes:
  • Oxidation states are shown with a + or – sign followed by the Arabic symbol for the number, e.g. +2, –1.
  • Examples should include hydrogen in metal hydrides (–1) and oxygen in peroxides (–1).
  • The terms “oxidation number” and “oxidation state” are often used interchangeably, and either term is acceptable in assessment.
  • Naming conventions for oxyanions use oxidation numbers shown with Roman numerals, but generic names persist and are acceptable. Examples include nitrate, nitrite, sulfate, sulfite.
Linking questions:
  • Reactivity 3.2 How can oxidation states be used to analyse redox reactions?
This video covers how to determine oxidation states.