Atom

How it is used

Atoms are about 10⁻¹⁰ m across, while the nucleus is roughly 100,000 times smaller. Physicists talk about atomic structure, models of the atom (Thomson, Rutherford, Bohr) and atoms that are excited, ionised or neutral. The adjective is 'atomic'.

Example sentences

1. Rutherford's experiment showed that the atom has a small, dense nucleus.

2. A neutral atom has the same number of electrons as protons.

Common collocations

• atomic structure
• atomic number
• neutral atom
• model of the atom
• excited atom

Related terms

• nucleusThe very small, dense centre of an atom, made of protons and neutrons. It contains almost all of the atom's mass and all of its positive charge.
• electronA very light particle with a negative charge of about −1.6 × 10⁻¹⁹ C, found around the nucleus of every atom. Moving electrons carry the current in metal wires.
• isotopeOne of two or more forms of the same element whose atoms have the same number of protons but different numbers of neutrons. Isotopes behave the same chemically but have different masses.
• energy levelOne of the fixed amounts of energy that an electron in an atom is allowed to have. Electrons move between levels by absorbing or emitting photons.
• photonA single packet, or quantum, of electromagnetic energy. Its energy depends only on the frequency of the radiation: E = hf, where h is Planck's constant.

This word in other fields

The same English word can have a different meaning in another field:

• atom · Chemistry

More terms: Atomic and Nuclear Physics

• radioactive decay
• half-life
• nuclear fission
• nuclear fusion