Biology Ch# 2.1

  1. Atoms
    All matter is composed of these
  2. Nucleus
    In all atoms

    positive charge
  3. Electrons
    One or more in each atom

    negatively charged

    moving in a cloud around nucleus
  4. Protons
    one or more found in nucleus

    positively charged
  5. Neutrons
    one or more are found in an atom's nucleus

    no charge
  6. Mass
    quantity of matter present

    > mass = > quantity of matter
  7. Dalton
    unit for measurement of a mass of a proton

    (atomic mass unit)
  8. Atomic Mass Unit
  9. Mass of proton/neutron
    1.7 x 10^-24 grams
  10. Mass of an electron
    9 x 10^28 grams
  11. Element
    pure substance

    contains only one kind of atom

    have certain properties and characteristics that distinguish them
  12. Proton #
    Atomic # (on top in periodic table)

    On top for 2H
  13. Mass #
    Protons + Neutrons

    # at bottom in periodic table
  14. Neutron #
    Mass # - Proton #

    top number (2H) - bottom # (1H)
  15. Isotopes
    Different version of an element that has the same # of protons but a different # of nuetrons
  16. Molecules
    stable associations that most atoms of living things are organized
  17. Orbital
    The region where the electrons are found
  18. Electron Shells (max orbitals)
    • First, S - 2
    • Second, P - 8
    • Third and beyond - 8
  19. Valence shell
    determines bonds

    outermost electron shell
  20. Octet Rule
    The tendency to have eight electrons in the Valence shell

    creates stability
  21. Stable
    an atom that cannot react with other atoms
Card Set
Biology Ch# 2.1
Chapter #2