The Periodic Table
Periodic Table hub covering groups, periods, Group 1 and 17 trends, noble gases, transition elements and the reactivity series.
Learning goals
- describe the Periodic Table as an arrangement of the elements in the order of increasing proton (atomic) number
- describe how the position of an element in the Periodic Table is related to proton number and electronic configuration
- describe the relationship between number of outer (valence) electrons and the ionic charge of an ion for the first twenty elements
- explain the similarities between the elements in the same group of the Periodic Table in terms of their electronic configuration
- describe the change from metallic to non-metallic character from left to right across a period of the Periodic Table
- describe the relationship between number of outer (valence) electrons and metallic/non-metallic character
- predict the properties of elements in Group 1 and Group 17 using the Periodic Table.
- describe lithium, sodium and potassium in Group 1 (the alkali metals) as a collection of relatively soft, low density metals showing a trend in melting point and in their reaction with water
- describe chlorine, bromine and iodine in Group 17 (the halogens) as a collection of diatomic non- metals showing a trend in colour, state and their displacement reactions with solutions of other halide ions
- describe the elements in Group 18 (the noble gases) as a collection of monoatomic elements that are chemically unreactive and hence important in providing an inert environment, e.g. argon and neon in light bulbs; helium in balloons; argon in the manufacture of steel
- describe the lack of reactivity of the noble gases in terms of their electronic configurations.
- describe typical transition elements as metals having high melting point, high density, variable oxidation state and forming coloured compounds
- state that the elements and/or their compounds are often able to act as catalysts (see also 10(d)).
- place in order of reactivity calcium, copper, (hydrogen), iron, lead, magnesium, potassium, silver, sodium and zinc by reference to the reactions, if any, of the metals with water, steam and dilute hydrochloric acid
- place in order of reactivity calcium, copper, (hydrogen), iron, lead, magnesium, potassium, silver, sodium and zinc by reference to — the reduction, if any, of their oxides by carbon and/or by hydrogen
- describe the reactivity series as related to the tendency of a metal to form its positive ion, illustrated by its reaction with — the aqueous ions of the other listed metals
- describe the reactivity series as related to the tendency of a metal to form its positive ion, illustrated by its reaction with — the oxides of the other listed metals
- deduce the order of reactivity from a given set of experimental results
- describe the action of heat on the carbonates of the listed metals and relate thermal stability to the reactivity series
- describe the ease of obtaining metals from their ores by relating the elements to their positions in the reactivity series
- describe the essential conditions for the corrosion (rusting) of iron as the presence of oxygen and water; prevention of rusting can be achieved by placing a barrier around the metal, e.g. painting; greasing; plastic coating; galvanising
- describe the sacrificial protection of iron by a more reactive metal in terms of the reactivity series where the more reactive metal corrodes preferentially, e.g. underwater pipes have a piece of magnesium attached to them.
The Periodic Table is a prediction tool. Its arrangement links proton number, electron configuration, group behaviour and recurring trends in chemical properties.
Jump to: Prerequisites · Quick Reference · Core knowledge · Sub-topics · Quiz
Prerequisites
Quick Recall
Revise these ideas before starting:
Interactive Periodic Table (Mobile-friendly)
Use the interactive table to search elements quickly and toggle between O Level and A Level fields.
Open Interactive Periodic TableQuick Reference
| Item | Quick rule / reminder |
|---|---|
| Arrangement | elements arranged by increasing proton number (Z), not relative atomic mass (Aᵣ) |
| Group | Groups 1 and 2 have 1 and 2 outer electrons; Groups 13–18 have 3–8 outer electrons (except helium, with 2); this shortcut does not apply to transition elements |
| Period | period number = number of occupied electron shells |
| Common ion charges (first 20) | Group 1: + 1; Group 2: + 2; Group 13: + 3; Group 14: no simple ions (C/Si usually covalent); Group 15: -3; Group 16: -2; Group 17: -1; Group 18: no common ions |
| Across a period | outer-electron count increases and character changes from metallic to non-metallic |
| Down a group | members retain the same outer-electron pattern, but the property trend depends on the group |
| Displacement (metals) | a more reactive metal displaces a less reactive metal from its salt solution |
| Displacement (halogens) | more reactive halogen displaces a less reactive halide; Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻ |
| Halogen observations (aqueous) | Cl₂(aq) pale green; Br₂(aq) orange; I₂(aq) brown |
| Trend reasons | Group 1: more reactive down (easier electron loss); Group 17: less reactive down (harder electron gain) |
Core knowledge to remember
- Group: vertical column; elements have similar chemical properties.
- Period: horizontal row; elements have the same number of shells.
- Valence electrons: electrons in the outermost shell.
- Alkali metals (Group 1): metals that form M⁺; react with water to form hydroxide + H₂.
- Halogens (Group 17): reactive diatomic non-metals that form X⁻ ions.
- Noble gases (Group 18): monatomic, very unreactive (full outer shell).
- Transition elements: high density/melting point; coloured compounds; variable ion charges; catalysts.
- Reactivity series: ranking by how easily metals form positive ions.
Sub-topics
Core trends and structure
The Periodic Law
Group/period meaning, ion charges, and key trends.
Metals and Non-Metals
Properties, ions formed, and oxide patterns.
Core groups
Group 1 Elements: The Alkali Metals
Softness, low density, melting-point trend and reactions with water.
Group 17 Elements: The Halogens
Displacement reactions and colour observations.
Noble Gases
Unreactivity, monatomic nature, and common uses.
Special metals
Transition Elements
Variable oxidation states, coloured compounds, catalysts.
Reactivity and applications
The Reactivity Series of Metals
Displacement, extraction, carbonate stability, rusting prevention.
Common mistakes
- Group number trap: it helps for main-group ions, but not for transition metals.
- Direction errors: Group 1 reactivity increases down; Group 17 reactivity decreases down.
- Displacement direction: only a more reactive element displaces a less reactive one (metals and halogens).
- Rusting conditions: rusting needs both oxygen and water (not one only).
- Atomic number vs mass: the table is arranged by proton number (Z), not Aᵣ.
- Helium duplet: helium has 2 electrons but still has a full outer shell (first shell max 2).
- Group 14 ions: carbon and silicon do not form simple ions in O-Level questions; do not write “±4” as a typical ion charge.
- Halogens are diatomic: write Cl₂, Br₂, I₂ (not Cl).
- Halogen displacement is redox: the halogen gains electrons (is reduced); the halide loses electrons (is oxidised).
Quiz
Practice (Quiz + Structured Questions)