Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want atomic structure and the periodic table — subatomic particles, isotopes and electron arrangements — to become a reliable source of marks instead of a number-crunching exercise.
What query it owns: how to understand and revise atomic structure and the periodic table in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the atomic-structure-and-the-periodic-table revision-guide angle, while Tutopiya’s Atomic Structure And The Periodic Table subtopic page owns the learning resource and the free Atomic Structure And The Periodic Table quiz owns the practice.

Atoms are the building blocks of all matter. Cambridge IGCSE Coordinated Science (0654) expects you to describe protons, neutrons and electrons, calculate numbers of subatomic particles, explain isotopes, and relate atomic number and period to the periodic table. This guide links each idea to what examiners reward.

Key takeaways

• Protons are positive (+1), in the nucleus; neutrons are neutral, in the nucleus; electrons are negative (−1), in shells.
• Atomic number (Z) = number of protons = number of electrons (in a neutral atom).
• Mass number (A) = protons + neutrons; neutrons = A − Z.
• Isotopes are atoms of the same element with different numbers of neutrons (same Z, different A).
• Electrons fill shells: 2, 8, 8 for the first three shells (up to calcium).

What is atomic structure in Cambridge IGCSE Coordinated Science?

Every atom has a tiny, dense nucleus containing protons and neutrons, surrounded by electrons in energy levels (shells). The atomic number tells you the element and the number of electrons in a neutral atom. The periodic table arranges elements by atomic number — elements in the same group have the same number of outer electrons; elements in the same period have the same number of electron shells.

You can read the full explanation, diagrams and notes on Tutopiya’s Atomic Structure And The Periodic Table subtopic page before you attempt questions.

Subatomic particles — properties and location

Particle	Relative charge	Relative mass	Location
Proton	+1	1	Nucleus
Neutron	0	1	Nucleus
Electron	−1	~1/1840 (negligible)	Electron shells

Key terms and formulas

Term	Symbol / formula	Meaning
Atomic number	Z	Number of protons (defines the element)
Mass number	A	Protons + neutrons
Neutrons	A − Z	Calculated from mass and atomic number
Isotope	Same Z, different A	Same element, different neutron count

Atomic structure in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical atomic structure stem
State	Give a value or fact	”State the number of protons in a sodium atom.”
Calculate	Work out subatomic particles	”Calculate the number of neutrons in ³⁷Cl.”
Define	Give precise meaning	”Define the term isotope.”
Write electronic configuration	Show electron arrangement	”Write the electronic configuration of magnesium.”

Worked exam-style stems (how to answer the wording)

1. “An atom has atomic number 11 and mass number 23. Calculate the number of neutrons.” Neutrons = A − Z = 23 − 11 = 12. Mark-scheme reward: correct subtraction and answer.
2. “Define the term isotope.” Atoms of the same element (same number of protons) with different numbers of neutrons / different mass numbers. Reward: same element and different neutrons.
3. “Write the electronic configuration of an atom of chlorine (Z = 17).” 2.8.7 (or 2, 8, 7 electrons in shells). Reward: correct shell arrangement totalling 17 electrons.

Test yourself with the Atomic Structure And The Periodic Table quiz once you can calculate subatomic particles and write configurations.

How atomic structure connects to the rest of Coordinated Science

Atomic structure leads directly into Ions And Ionic Bonds and Molecules And Covalent Bonds — electron arrangements determine bonding. It also underpins the periodic table and Stoichiometry. The Cambridge IGCSE Coordinated Science resource hub links every subtopic.

Common mistakes students make

• Confusing atomic number with mass number.
• Calculating neutrons as A + Z instead of A − Z.
• Saying isotopes have different numbers of protons (they have different neutrons).
• Forgetting electrons = protons only in a neutral atom.
• Writing electronic configurations that do not add up to the atomic number.

When you need more support

If atomic structure questions keep costing marks, work through the Atomic Structure And The Periodic Table quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is atomic structure hard in Coordinated Science? The particle model is manageable — marks are lost on neutron calculations and confusing isotopes with different elements.

What is the difference between atomic number and mass number? Atomic number is the number of protons; mass number is protons plus neutrons.

What are isotopes? Atoms of the same element with the same number of protons but different numbers of neutrons.

How do I revise atomic structure effectively? Practise A − Z calculations, write configurations for the first 20 elements, then take the Atomic Structure And The Periodic Table quiz.

Ready to master Cambridge IGCSE Coordinated Science atomic structure?

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