The nucleus Flashcards – Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028)

What are nucleons?

The protons and neutrons in an atomic nucleus.

What are the relative charges of a proton, a neutron and an electron?

Proton: $+1$; neutron: $0$; electron: $-1$.

Where are electrons located relative to the atomic nucleus?

Outside the nucleus.

What is the proton number, or atomic number, $Z$?

The number of protons in the nucleus.

What does the proton number identify?

The element.

What is the nucleon number, or mass number, $A$?

The total number of protons and neutrons in the nucleus.

How is the number of neutrons calculated from the nucleon number $A$ and proton number $Z$?

$A-Z$

In nuclide notation ${}^{A}_{Z}\mathrm{X}$, what do $A$, $Z$ and $\mathrm{X}$ represent?

$A$: nucleon number; $Z$: proton number; $\mathrm{X}$: element symbol.

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

Why do isotopes of the same element have different nucleon numbers?

They have different numbers of neutrons, while their proton numbers are the same.