# Proton

A particle inside the nucleus of an atom with a positive charge. Its relative mass is 1.

Chemistry (school) · Part 01: Atoms and matter · Card 5 of 10 · Last updated 2026-10-19

## Analogy

Protons are like the plus ends of tiny batteries, packed in the centre.

## In practice

The number of protons decides which element an atom is. Six protons always means carbon.

## Practice

### Flashcards

- **What is the charge and relative mass of a proton?** Charge +1 and relative mass 1.
- **Why is a neutral atom neutral?** It has the same number of positive protons and negative electrons.

### Interview questions

**Explain what is the same and what is different about two isotopes of an element.**

- Same number of protons
- Same number of electrons when neutral
- Different number of neutrons
- Different mass number

## Questions people ask

### Why does the number of protons decide the element?

The number of protons fixes how many electrons a neutral atom has, and electrons control how the atom reacts. So the proton count gives each element its own chemistry. Change the number of protons and you get a different element, such as nitrogen instead of carbon.

### Where are protons found in an atom?

Protons sit in the nucleus, the tiny dense centre of the atom, together with the neutrons. The nucleus is about ten thousand times smaller than the whole atom, yet holds almost all its mass. The electrons move around it in the space outside.

## Related concepts

- [Neutron](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-1/chemistry-school-part-1-concept-6)
- [Electron](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-1/chemistry-school-part-1-concept-7)
- [Atom](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-1/chemistry-school-part-1-concept-1)
- [Isotope](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-1/chemistry-school-part-1-concept-10)

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