Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want the nuclear atom — protons, neutrons, electrons and isotopes — to become a reliable source of marks instead of a jumble of numbers and charges.
What query it owns: how to understand and revise the nuclear atom in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the nuclear-atom revision-guide angle, while Tutopiya’s The Nuclear Atom subtopic page owns the learning resource and the free The Nuclear Atom quiz owns the practice.

The nuclear atom has a tiny, dense, positively charged nucleus (protons and neutrons) surrounded by electrons in shells. Cambridge IGCSE Coordinated Science (0654) expects you to state subatomic charges and masses, define isotopes, and describe Rutherford’s scattering experiment. This guide links each concept to the definition and explanation questions examiners set.

Key takeaways

• Proton: charge +1, relative mass 1, in nucleus.
• Neutron: charge 0, relative mass 1, in nucleus.
• Electron: charge −1, negligible mass, in shells outside nucleus.
• Mass number (A) = protons + neutrons; atomic number (Z) = protons only.
• Isotopes: same atomic number, different number of neutrons.

What is the nuclear atom in Cambridge IGCSE Coordinated Science?

Atoms consist of a central nucleus containing protons and neutrons, with electrons orbiting in energy levels. The nucleus is extremely small but contains almost all the atom’s mass. Rutherford’s alpha-particle scattering showed that most of the atom is empty space and that a dense positive nucleus exists. Isotopes of an element have the same number of protons but different numbers of neutrons.

You can read the full explanation, diagrams and notes on Tutopiya’s The Nuclear Atom subtopic page before you attempt questions.

Subatomic particles compared

Particle	Location	Relative charge	Relative mass
Proton	Nucleus	+1	1
Neutron	Nucleus	0	1
Electron	Shells	−1	1/1840 (≈ 0)

Atomic notation and isotopes

Symbol part	Meaning	Example (carbon-12)
Z (bottom)	Atomic number = protons	6
A (top)	Mass number = p + n	12
Neutrons	A − Z	12 − 6 = 6
Isotope	Same Z, different A	¹²C and ¹⁴C both have 6 protons

The nuclear atom in past-paper wording

Command word	What the question wants	Typical stem
Define	Isotope or atomic number	”Define the term isotope.”
State	Particle properties	”State the charge on a neutron.”
Describe	Rutherford experiment	”Describe the alpha-particle scattering experiment.”
Explain	Conclusions from scattering	”Explain what the scattering results show about the atom.”

Worked exam-style stems

1. “An atom has 11 protons and 12 neutrons. State its mass number and number of electrons (neutral atom).” Mass number = 11 + 12 = 23; electrons = 11 (equals protons). Reward: A = 23 and 11 electrons.
2. “Define isotope.” Atoms of the same element with the same number of protons but different numbers of neutrons. Reward: same protons + different neutrons.
3. “Explain why most alpha particles passed straight through the gold foil.” The atom is mostly empty space; the nucleus is very small compared to the atom. Reward: mostly empty space.

Test yourself with the The Nuclear Atom quiz once you can define isotopes and interpret nuclear symbols.

How the nuclear atom connects to the syllabus

Atomic structure leads directly to Radioactivity — unstable nuclei emit radiation. It also links to chemistry atomic structure topics. The Cambridge IGCSE Coordinated Science resource hub links every Atomic Physics subtopic.

Common mistakes students make

• Confusing atomic number (protons) with mass number (protons + neutrons).
• Saying isotopes have different numbers of protons (they have different neutrons).
• Giving electrons a relative mass of 1 (mass is negligible).
• Forgetting a neutral atom has equal protons and electrons.
• Stating electrons are inside the nucleus.

When you need more support

If nuclear atom definition and Rutherford questions keep costing marks, work through the The Nuclear Atom quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is the nuclear atom hard in Coordinated Science? Learn particle charges and masses, isotope definition, and Rutherford’s conclusions — that covers most questions.

What is an isotope? Atoms of the same element with the same number of protons but different numbers of neutrons.

What did Rutherford’s experiment show? The atom has a small, dense, positively charged nucleus with mostly empty space around it.

How do I revise the nuclear atom effectively? Practise reading nuclear symbols, define isotopes, describe Rutherford scattering, then take the quiz.

Ready to master Cambridge IGCSE Coordinated Science the nuclear atom?

Start with the The Nuclear Atom subtopic page, then book a free trial with a Cambridge IGCSE Coordinated Science specialist to turn atomic structure knowledge into guaranteed marks.

Ready to Excel in Your Studies?

Get personalised help from Tutopiya's expert tutors. Whether it's IGCSE, IB, A-Levels, or any other curriculum — we match you with the perfect tutor and your first session is free.

Book Your Free Trial