1dPrinciples of Chemistry

The Periodic Table — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions

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Lesson summary

The Periodic Table Edexcel O Level Linear Chemistry notes: understand how elements are arranged in the Periodic Table: - in order of atomic number - in groups and periods.Na burns with yellow flame; Mg with white flame.ChloridesNaCl, MgCl₂ ionic (neutral); AlCl₃, SiCl₄, PCl₅ hydr…

Melting point
The Periodic Table Edexcel O Level Linear Chemistry: what to do next
Periodicity
Atomic radius
Electronegativity
Amphoteric

Section 1 of 12Process & sequence

Trends across Period 3

Atomic radius decreases (more protons, same shielding)

First IE generally increases

Electrical conductivity falls after Al

1Oxides change basic2amphoteric3acidic

Section 2 of 12Keep going

The Periodic Table Edexcel O Level Linear Chemistry: what to do next

These The Periodic Table Edexcel O Level Linear Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your The Periodic Table Edexcel O Level Linear Chemistry understanding with the practice questions below, then reread any The Periodic Table Edexcel O Level Linear Chemistry point you were unsure about before moving on.

Practice: The Periodic Table Edexcel O Level Linear Chemistry practice questions

Previous lesson: 1c Atomic structure — Notes

Next lesson: 1e Chemical formulae, equations and calculations — Notes

Course: Edexcel Linear – OL (chemistry) — all units

Official syllabus: Pearson Edexcel International GCSEs

Section 3 of 12Similar properties within a group

Elements in the same group have similar chemical properties because they have the same number of outer-shell electrons, so they react and bond in the same way.

Similar properties within a group

The group number gives the number of outer electrons (except for helium in Group 0, which has only one shell holding 2 electrons).

Observing one element in a group lets you predict how the others react,

and reacting two or more elements of a group allows trends in reactivity to be established.

Section 4 of 12Reactivity trends

Lithium, sodium and potassium (Group 1) all react with Group 7 elements to form ionic compounds.

Reactivity trends

Group 1 metals become more reactive down the group,

because the outer electron is further from the nucleus and more shielded,
so it is lost more easily.

Group 7 elements become less reactive down the group, because an incoming electron is attracted less strongly to a larger atom.

Reactions of an element depend on the number of outer-shell electrons: metals tend to lose them to form positive ions,

while non-metals gain or share them.

Group	Outer electrons	Tendency	Ion
1	1	Lose 1 electron	1+
2	2	Lose 2	2+
6	6	Gain 2	2-
7	7	Gain 1	1-
0	8 (He 2)	None (full shell)	No ion

The pattern can be expressed in terms of attraction: in Group 1 the outer electron is shielded by more inner shells as you go down, so it is held less strongly and lost more readily.

Reactivity trends

In Group 7 the incoming electron is added to a shell further from the nucleus, so it is attracted less strongly.

This is why chlorine displaces bromide and iodide ions but not the other way round.

Section 5 of 12Why noble gases are unreactive

The Group 0 elements are the noble gases.

Why noble gases are unreactive

They are non-metals, monatomic (exist as single atoms), and are colourless, non-flammable gases at room temperature.

Most elements react to complete their outer shell by losing, gaining or sharing electrons.

Noble gases already have full outer shells and so do not need to react; they are unreactive (inert) and do not form molecules easily.

Electronic configurations

He = 2;
- Ne = 2,8;
- Ar = 2,8,8;
- Kr = 2,8,18,8;
- Xe = 2,8,18,18,8.
Most have 8 outer electrons;
- helium has 2.
You do not need to know specific uses, but many applications rely on their inertness, such as argon in filament lamps to stop the filament burning away and helium in balloons because it is less dense than air and non-flammable.

Section 6 of 12Applying the ideas

Typical exam answers combine position and configuration.

Applying the ideas

For example: "Potassium is more reactive than sodium.

Both have one outer electron,

but the outer electron of potassium is in a shell further from the nucleus,
so it is lost more easily." Or "Argon is unreactive because its outer shell is full,
so it has no tendency to gain, lose or share electrons." Link each property to electronic structure, not to the name of the group alone.

Practice question style

"Explain why lithium and sodium both react with water to form an alkaline solution." Answer: each has one outer electron, which it loses to form a 1+ ion;
- the metal hydroxide formed dissolves to give OH^- ions so the solution is alkaline.
Use group number, outer electrons and electronic configuration in your reasoning.

Section 7 of 12Compare

Period 3 elements and their oxides
Element	Structure	Oxide	Oxide bonding	Oxide + water	Acid/base nature
Na	Giant metallic	Na₂O	Ionic	NaOH, pH 13–14	Basic
Mg	Giant metallic	MgO	Ionic	Mg(OH)₂, pH 9	Basic
Al	Giant metallic	Al₂O₃	Ionic/covalent	Insoluble	Amphoteric
Si	Giant covalent	SiO₂	Giant covalent	Insoluble	Acidic (with hot NaOH)
P	Simple molecular (P₄)	P₄O₁₀	Covalent	H₃PO₄, pH 2	Acidic
S	Simple molecular (S₈)	SO₂ / SO₃	Covalent	H₂SO₃ / H₂SO₄, pH 1–2	Acidic
Cl	Simple molecular (Cl₂)	Cl₂O₇	Covalent	HClO₄	Acidic

Section 8 of 12Worked examples

Explain why sodium and potassium have similar reactions. [1]1 mark
Explain why potassium is more reactive than lithium. [2]2 marks
Give the electronic configuration of argon and explain why it is unreactive. [2]2 marks
State two properties of the noble gases. [2]2 marks

Section 9 of 12Key terms

Term	Meaning
Noble gas	Group 0 element with a full outer shell.
Monatomic	Existing as single atoms.
Inert	Unreactive.
Outer shell	Highest energy shell holding electrons.
Reactivity	How readily an element undergoes reactions.

Section 10 of 12Syllabus checklist

understand how elements are arranged in the Periodic Table: - in order of atomic number - in groups and periods.

understand how to deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table

understand how to use electrical conductivity and the acid-base character of oxides to classify elements as metals or non-metals

identify an element as a metal or a non-metal according to its position in the Periodic Table

understand how the electronic configuration of a main group element is related to its position in the Periodic Table

understand why elements in the same group of the Periodic Table have similar chemical properties

understand why the noble gases (Group 0) do not readily react

Section 11 of 12Command terms

Command terms

Give / State / Name

Recall a fact; one idea per mark.

Define

Give the exact meaning using the specification keywords.

Describe

Give an account of what happens / the pattern in data, quoting values; no reasons needed.

Explain

Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.

Suggest

Use knowledge in a new context; more than one answer may be accepted.

Compare

Similarities and differences; each point must refer to both items.

Calculate

Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.

Discuss

Explore the issue from different angles and link the points.

Evaluate / Assess

Weigh strengths and weaknesses and reach a supported judgement.

Deduce

Draw a conclusion from the information given.

Justify

Support a statement/choice with evidence.

Section 12 of 12Exam technique

Saying noble gases have no electrons in the outer shell — they have a full shell.

Saying reactivity of Group 7 increases down the group.

Forgetting helium has 2 outer electrons.

Giving a trend without a reason.

Last updated: 18 October 2026