Working Definitions, Exam 1

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Working Definitions, Exam 1
2012-08-29 01:24:52
chem 201

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  1. atomic number (Z)
    • the number of protons in the nucleus
    • determines the identity of an atom
  2. element
    • an atom of specific identity or a number of atoms of the same identity
    • 114 confirmed (1-112, 114, 116)
  3. mass number (A)
    • the sum of the number of protons and neutrons in the nucleus
    • not a true mass; just a count of the number of protons and neutrons
  4. isotope
    • an atom of an element with a specific number of neutrons
    • different number of isotops for a single element
    • can be natural or man-made
    • number of neutrons differ, number of protons stay the same
  5. natural abundance / percent abundance
    the fractional amount (percent) of one isotope relative to all isotopes for one element as found naturally on earth
  6. atomic mass
    • the mass of an element averaged over the distribution of its isotopes
    • unit = u (previously amu)
    • super small! (1 u = 1.6605 x 10-24 g [GIN])
    • term can be used interchangably with atomic weight
  7. atomic weight
    • the relative atomic mass
    • expressed as a number without units
    • term can be used interchangably with atomic mass
  8. elemental form
    a specific form of an element
  9. compound
    a substance composed of two or more elements
  10. monatomic
    • composed of only one atom
    • includes only noble gases (when neutral)
  11. polyatomic
    • composed of two or more atoms
    • joined together by different types of chemical bonds
  12. diatomic
    composed of two atoms
  13. network
    • an elemental form or a compound in which chemical bonds extend continuously in one/two/three dimensions
    • no specific molecule or form
    • includes all metals
  14. molecule
    • a neutral assembly of two or more atoms bonded together
    • specific number, specific atom, in a specific arrangement
  15. allotropes
    • different elemental forms of the same element
    • ex: O2 and O3
  16. ionic compound
    a compound composed of ions
  17. ion
    • a monatomic or polyatomic chemical unit with a charge
    • not an elemental form anymore
    • include superscript charge information in the formula
    • if # protons =/= # electrons --> unit carries a charge
  18. cation
    • an ion with a positive charge
    • # p+ > # e--
  19. anion
    • an ion with a negative charge
    • # p+ < # e--
  20. ionic bond
    • the +/-- attraction of cations and anions
    • ex: NaCl (Na+ and Cl--)
  21. covalent bond
    • a bond involving shared electrons
    • overlapping shared electrons are dispersed in that shared region
    • all metals held together by this bond
    • counts as a network
    • if a compound has both an ionic and covalent bond, it is considered ionic
    • if a compound uses only covalent bonds, it is considered covalent
  22. isomers
    different chemical units with the same formula but with a different arrangement of atoms
  23. formula unit
    • the number and types of atoms given by the formula
    • just a general term