Skip to main content
Pearson+ LogoPearson+ Logo
Back

Atoms- Smallest Unit of Matter definitions

7 students found this helpful
Control buttons has been changed to "navigation" mode.
1/15
  • Atom
    The smallest unit of matter, consisting of a nucleus surrounded by electrons.
  • Matter
    Anything that takes up space and has mass, including living and non-living things.
  • Chemical Element
    A pure substance made up of only one type of atom.
  • Proton
    A subatomic particle with a positive charge found in the nucleus of an atom.
  • Neutron
    A subatomic particle with no charge found in the nucleus of an atom.
  • Electron
    A subatomic particle with a negative charge orbiting the nucleus of an atom.
  • Atomic Number
    The total number of protons in the nucleus of an atom, defining the element.
  • Mass Number
    The total number of protons and neutrons in the nucleus of an atom.
  • Energy Shell
    Regions around the nucleus where electrons are likely to be found.
  • Valence Shell
    The outermost energy shell of an atom, containing valence electrons.
  • Valence Electrons
    Electrons in the outermost energy shell, involved in chemical bonding.
  • Octet Rule
    Atoms are more stable and less reactive when their valence shells are full.
  • Atomic Mass Unit
    A unit of mass used to express atomic and molecular weights.
  • Periodic Table
    A table arranging all known elements based on their chemical properties.
  • Bulk Elements
    Elements that make up the majority of living organisms, such as CHNOPS.