Science
What is Atom?
An atom is the smallest unit of an element that still has its chemical properties — the basic building block of all ordinary matter. Each atom has a dense central nucleus of protons and neutrons, surrounded by a cloud of much lighter electrons.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains atom.
Key things to understand
- 1An atom has three main particles: positively charged protons and neutral neutrons in the nucleus, and negatively charged electrons around it.
- 2The number of protons (the atomic number) decides which element it is — 1 proton is hydrogen, 6 is carbon, 79 is gold.
- 3Atoms are mostly empty space: the nucleus is tiny compared with the electron cloud around it.
- 4Atoms join by sharing or swapping electrons to form molecules and compounds.
- 5Atoms are astonishingly small — millions would fit across the width of a human hair.
Frequently asked questions
- What is an atom made of?
- Protons and neutrons packed into a central nucleus, with electrons moving around it. Protons are positive, electrons negative, and neutrons carry no charge.
- What's the difference between an atom and a molecule?
- An atom is a single building block; a molecule is two or more atoms bonded together — like two hydrogen atoms and one oxygen atom forming a water molecule.
- Can you see an atom?
- Not with the naked eye or a normal microscope — atoms are far too small. Special instruments like scanning tunneling microscopes can image them indirectly.