S10 2: Atomic Theories, Atoms, Ions

• John Dalton's atomic theory:

  • Modelled the atom as a sphere, similar to a billiard ball
  • Matter is composed of indestructible, indivisible atoms
  • Atoms are different for each element
• J. J. Thompson's atomic model:

  • Proposed the "plum pudding model" where negatively charged particles are embedded in a positively charged sphere
• Ernest Rutherford's atomic model:l

  • Discovered the nucleus, which is positively charged
  • Identified the positively charged subatomic particle as the proton
• Subatomic particles:

  • Electron (e-), Proton (p+), Neutron (n0)
  • Electrons are negatively charged, protons are positively charged
  • In atoms, the number of electrons and protons are the same, resulting in a net electrical charge of 0
  • In ions, atoms gain or lose electrons to become charged
  • Nonmetals gain electrons to become negative anions, metals lose electrons to become positive cations
• Isotopes:

  • Atoms of the same element with different masses
  • Atoms can have different masses by changing the number of neutrons
• Niels Bohr's atomic model:

  • Electrons orbit the nucleus in different energy levels
  • Proposed the "planetary model" with a maximum number of electrons in each energy level equal to the number of elements in the period
• Ions:

  • Charged elements formed by losing or gaining electrons
  • Positive ions lose electrons, negative ions gain electrons
  • Positive ions are cations, negative ions are anions
  • Valence electrons are in the outer energy level
• Naming Ions

  1. nonmetal = “ide”and add the word "ion" after it
  2. metal, = same and add theword “ion” after it.