What Is an Atom?
The smallest particle of an element.
What this lesson covers
Why it matters
Keep cutting a lump of carbon in half, again and again, until you reach a single carbon atom — the smallest piece that is still carbon.
Predict first
What is the smallest particle of an element that still has its properties?
Every element is built from incredibly tiny atoms. An atom has a nucleus of protons (and neutrons) with electrons around it — and the number of protons names the element.
- An atom — correct
- A tiny drop
- A grain of dust
What you do
Build a carbon atom — add 6 protons, 6 electrons and 6 neutrons (carbon-12). The proton count is the atom's identity; protons + neutrons give its mass number 12.
Check yourself
What decides which element an atom is?
The proton number (atomic number) is the element's identity.
An atom is best described as…
Atoms are the tiny building blocks of elements, far too small to see.
Are atoms truly the smallest possible particles?
Atoms are the smallest particle that is still the element, but they are built from even smaller subatomic particles.
- the number of protons — correct
- the number of neutrons
- its colour
- the smallest particle of an element that keeps its properties — correct
- just visible under a hand lens
- a kind of mixture
- No — atoms are made of smaller protons, neutrons and electrons — correct
- Yes, atoms cannot be divided at all
- Yes, nothing exists inside an atom