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Atoms- Smallest Unit of Matter definitions

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  • Atom
    Smallest unit of matter, forming both living and nonliving things, and composed of subatomic particles.
  • Matter
    Anything that occupies space and has mass, including all living and nonliving substances.
  • Chemical Element
    Pure substance made of only one type of atom, defining the basic building blocks of matter.
  • Proton
    Positively charged subatomic particle located in the nucleus, determining the identity of an element.
  • Neutron
    Electrically neutral subatomic particle found in the nucleus, contributing to atomic mass.
  • Electron
    Negatively charged subatomic particle orbiting the nucleus in energy shells, involved in chemical bonding.
  • Nucleus
    Central region of an atom containing protons and neutrons, accounting for most of its mass.
  • Atomic Number
    Total number of protons in the nucleus, uniquely identifying each chemical element.
  • Mass Number
    Sum of protons and neutrons in the nucleus, representing the mass of a single atom.
  • Atomic Mass
    Average mass of all atoms of an element, reflecting natural isotope abundance.
  • Electron Orbital
    Three-dimensional region around the nucleus where electrons are likely to be found.
  • Energy Shell
    Layer surrounding the nucleus where electrons reside, with each shell holding a set number of electrons.
  • Valence Shell
    Outermost energy shell of an atom, containing electrons that determine chemical reactivity.
  • Valence Electron
    Electron located in the outermost energy shell, crucial for forming chemical bonds.
  • Octet Rule
    Principle stating atoms are most stable when their valence shell holds eight electrons.
  • Bulk Element
    Element required in large amounts for life, such as those remembered by the acronym CHNOPS.
  • Trace Element
    Element essential for life but needed only in very small quantities.