atoms

• Atom


  Fundamental particle of matter
• Element


  Pure substance made up of one type of atom
• There are 118 elements
• Pure element


  Has one kind of atom
• The most common gases in the universe are hydrogen and nitrogen
• Atomic Number (Z)


  Number of protons in the nucleus of an atom
• Mass Number (A)


  Number of protons + number of neutrons in the nucleus of an atom
• Hydrogen atom is an exception to the rule that atomic number = number of protons
• Isotopes of Carbon


  • C-12
  • C-13
  • C-14
• Electron Configuration


  Arrangement of electrons in an atom's shells and subshells
• Electron Shell Numbers


  • 1
  • 2
  • 3
  • 4
• Maximum number of electrons in each shell

  • 2
  • 8
  • 18
  • 32
• The atomic number of sodium is 11 and its mass number is 23. It contains 11 protons, 11 electrons, and 12 neutrons.
• Potassium has an electron configuration of 2.8.8.1, which is an exception to the general rule
• Azimuthal Quantum Number (l)

  Determines the shape of the orbital
• Orbital shapes


  • s
  • p
  • d
  • f
• The 4s orbital has a lower energy than the 3d orbital