GCSE · Chemistry · AQA · Spec 8462

The periodic table

One table organises every element ever discovered — and predicts chemistry you haven't seen yet.

What you need to know

  • Elements are arranged in order of increasing atomic (proton) number.
  • Horizontal rows are periods; vertical columns are groups. Similar properties repeat periodically.
  • Elements in the same group have the same number of outer-shell electrons, giving them similar chemical properties.
  • Metals are found to the left and bottom of the table; non-metals are found to the right and top.

The big picture

The periodic table arranges all known elements in order of increasing atomic (proton) number. Elements are organised into horizontal periods and vertical groups, and the word 'periodic' reflects the fact that elements with similar properties recur at regular intervals. An element's position in the table directly reveals how its electrons are arranged in shells, which in turn determines its chemical behaviour. Metals sit to the left and towards the bottom; non-metals cluster towards the right and top.

TONIGHT'S REVISION

The Periodic Table

How atomic structure determines every element's position — and its chemistry.

Chemistry · Periodic table

Explore the periodic table

Tap a lens to reveal the pattern. Tap an element to read its electron structure.

SelectedNaSodium
Atomic no.11
Mass23.0
Group · Period1 · 3
TypeAlkali metal

Tap any cell to load its data into the panel. Tap a lens to highlight a chemical family.

Exam line: For Groups 1–7, an element's group = number of outer-shell electrons (Group 0 has a full outer shell instead); its period = number of shells. These facts unlock position questions.
Watch out: Students often swap period and group. Period is the horizontal row (= shells); group is the vertical column (= outer electrons).

Predict, then check

Think about what the group number actually tells you before you tap.

Lithium (Li), sodium (Na), and potassium (K) are all in Group 1. A newly discovered element is placed in Group 1, Period 5. What can you predict about its chemistry — and why?

Metals vs non-metals — position predicts the reaction

Sodium is a metal on the left of the table; oxygen is a non-metal on the right. Their positions predict what they do.

Tap a molecule to see what it does in the reaction.

Why does position predict chemistry?

?

Reason it through

Why does knowing an element's group tell you how it will react?

Link 1 of 3

First link · your turn

What does the group number actually measure inside the atom?

2
Locked — reveal the link above first
3
Locked — reveal the link above first

Relationship matrix

Tap any cell to reveal it. Tap a column header to read one property down every item.

Outer-shell electronsPeriod if in row 3Metal or non-metal?Reacts similarly to…
Group 1 elemente.g. lithium, Li
Group 2 elemente.g. magnesium, Mg
Group 6 elemente.g. sulfur, S

Each cell hides a short answer and the reason behind it. Predict before you tap.

Cross-subject · Exam skill

Command words — periodic table questions

AQA exam questions use these command words on this topic. Know what each one demands.

PredictBloom · Apply

01Definition

Use your knowledge of the periodic table to say what will happen — you must give a reason based on electron structure or group position.

02Mark-band signal

A bare prediction with no reason scores 1 mark; adding 'because it is in the same group / has the same outer-shell electrons' earns the second mark.

03Sentence stems

  • Predict whether element X is a metal or non-metal. Give a reason.
  • Predict how element X will react compared to element Y in the same group.
  • Use the periodic table to predict a property of element Z.

04Common mistake

Students predict correctly but forget to give the electron-structure reason — losing the second mark.

Exam line: On AQA, 'Predict' questions almost always require a reason grounded in group number and outer-shell electrons — two marks means statement + reason.
Watch out: Never answer a 'Predict' question with just a yes/no or a bare statement — AQA mark schemes require the electron-structure justification for full marks.

Key points

1Atomic (proton) number increases left to right, top to bottom across the whole table.
2Period number = number of occupied electron shells in an atom of that element.
3Group number = number of outer-shell electrons for Groups 1–7; Group 0 elements have a full outer shell (helium has 2, the others have 8).
4Same group = same outer-shell electron count = similar reactions.
5Left/bottom = metals (form positive ions); right/top = non-metals (do not form positive ions).

Worked example

Problem

An element has the electron configuration 2, 8, 6. Use this to identify its period, its group, and predict whether it is a metal or a non-metal.

🧠

Memory hook

Think of the table as a block of flats: the floor you live on (period) tells you how many shells you have; your flat number in that row (group) tells you how many electrons are on the top floor. Neighbours in the same column share a top-floor count — and sharing a top-floor count means sharing a chemical personality.

★ Exam tip

AQA questions often ask you to 'use the periodic table to predict' something. Always state the group number, explain that it equals the number of outer-shell electrons, and link that directly to the property or reaction asked about — examiners want the electron-structure reasoning, not just a description of position.

⚠ Watch out

Confusing period number with group number — remember: period = number of shells (horizontal row), group = outer-shell electrons (vertical column).

✓

Check yourself

Without looking: an element is in Period 2, Group 1. How many electron shells does it have, and how many electrons are in its outer shell?

Flashcards

(23)
In what order are elements arranged in the periodic table?
In order of increasing atomic (proton) number.
What is a period in the periodic table?
A horizontal row of elements.
What is a group in the periodic table?
A vertical column of elements.
Why is the table called 'periodic'?
Because elements with similar properties recur at regular intervals.
What does the period number tell you about an atom?
The number of occupied electron shells the atom has.
What does the group number tell you about an atom?
For Groups 1–7, the number of electrons in the outermost shell (Group 0 elements have a full outer shell).
Why do elements in the same group have similar chemical properties?
They have the same number of electrons in their outer shell.
Where are metals found in the periodic table?
To the left and towards the bottom.
Where are non-metals found in the periodic table?
Towards the right and top.
How do metals differ from non-metals in terms of ion formation?
Metals form positive ions; non-metals do not form positive ions.
An element has electron configuration 2, 8, 1. What period and group is it in?
Period 3, Group 1.
An element is in Period 2. How many electron shells does it have?
Two occupied electron shells.
An element is in Group 2. How many outer-shell electrons does it have?
Two outer-shell electrons.
How can you predict whether two elements will react similarly?
If they are in the same group, they have the same number of outer-shell electrons and will react in similar ways.
What is the atomic (proton) number of an element?
The number of protons in the nucleus of an atom of that element.
An element has 11 protons and electron configuration 2, 8, 1. Which period and group?
Period 3, Group 1.
Why does position in the periodic table allow predictions about chemical behaviour?
Because position is linked to electron arrangement, and electron arrangement determines how an element reacts.
An element is in the top-right region of the periodic table. Is it likely a metal or non-metal?
Non-metal — non-metals are found towards the right and top.
An element is in Period 3, Group 2. How many electrons does it have in total?
12 electrons (electron configuration 2, 8, 2 — proton number 12).
What links atomic number to electron configuration for neutral atoms?
The atomic number equals the total number of electrons in a neutral atom; electrons fill shells in order.
An element is in Period 4, Group 1. How many shells does it have?
Four occupied electron shells.
Two elements are in the same period but different groups. What do they share?
The same number of occupied electron shells (the same period number).
An element forms a positive ion easily. Where in the table would you expect to find it?
Towards the left and bottom — the metal region.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

Learn The periodic table properly — interactive practice, marked questions and flashcards.

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