chemistry 1.2

• Atom


  Meaning "uncuttable" in Greek
• Atoms


  • Made up of protons, neutrons and electrons (Year 9)
  • Protons = positive charge, found inside the nucleus, has a mass of 1 amu
  • Neutrons = neutral or no charge, found inside the nucleus, has a mass of 1 amu
  • Electrons = negative charge, found orbiting the nucleus, has a 5.48x10-4 amu

  
• Elements


  Different types of atoms
• Atomic number


  Indicates the number of protons in an element

  
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Changing the number of neutrons does not change the element
• Isotopes of carbon


  • All have the same number of protons (6)

  
• Ions


  Atoms with an unequal number of electrons and protons, resulting in a positive or negative charge

  
• Neutral atom


  Has an equal number of electrons and protons
• Anion


  Negatively charged ion with more electrons than protons
• Cation


  Positively charged ion with more protons than electrons
• Electron orbitals


  • Electrons orbit the nucleus in shells/energy levels
  • Shells have a maximum number of electrons: 2, 8, 18, 32

  
• Electron configuration notation


  Represents the number of electrons in each shell, e.g. 2,4

  
• Subshells within energy levels

  • s (2 electrons)
  • p (6 electrons)
  • d (10 electrons)
  • f (14 electrons)

  
• Valence electrons


  Electrons in the outermost shell of an atom
• Electron energy level transitions

  1. Electrons can gain energy and jump to a higher energy level

  2. Electrons fall back down to their prior energy level, emitting a photon (light)

  
• Flame colour test can be used to determine the composition of an unknown compound