Particle: definition in chemistry
Particle: A tiny piece of matter, such as an atom, molecule or ion, or a subatomic particle such as a proton, neutron or electron.
The particle model explains the states of matter: in solids particles are packed tightly and vibrate in place, in liquids they slide past one another, and in gases they move freely and far apart. Because particles are so small, chemists count them in large batches called moles. Subatomic particles set an atom's identity (protons), its isotope (neutrons) and its chemical behavior (electrons).
Examples
- Proton — positively charged, found in the nucleus
- Electron — negatively charged, about 1/1836 of a proton's mass
- Water molecule (H₂O) — a particle made of three atoms
- Sodium ion (Na⁺) — a charged particle
On the periodic table
An element's atomic number on the table is its number of protons, which in a neutral atom is also its number of electrons.