Atomic Structure

Atomic Structure

1. Classical atomic model

   • Dalton's atomic theory
     • Dalton's model : solid sphere
     • 1. Matter consists of tiny particles called atom.
     • 2. Atoms of one element are identical in mass.
     • 3. Compounds are the combination of atoms with a specific ratio.
     • 4.Chemical reactions involve reorganization of the atoms.
   • Thomson's atomic model
     • Raisin in the plum pudding
     • Experiment with cathode ray and conclude that matters consist of negatively charged particle called electron.
     • Calculate mass/charge ratio of electron = -5.686 * 10^12 kg/C
   • Rutherford's atomic model
     • Suggest the atomic nuclear model from the results of bombardment gold foil with alpha particles.
     • Atom consists of electrons which move around the positively charged center called nucleus.
     • atomic planetary model
     • Atom is mostly empty space. The size of nucleus is very small compare to the atom itself.

2. Quantum View of Atom

   • Bohr's model
     • Bohr proposed that atom has energy levels as circular orbits. Electrons move as wave in a specific energy levels. Electrons can transfer to different energy levels when they lose or gain energy.
     • Each energy level has specific quantum number (n) starts from 1,2,3...
   • Erwin Schrödinger used Quantum Mechanics to explain the energy state in the hydrogen atom.
     • The equation is called wave function. A specific wave function is often called an orbital.
       • Quantum number and atomic orbitals
         • the principal quantum number (n)
           • n = 1,2,3... small n, small size, close to nucleus, low energy
         • the orbital angular momentum quantum number (l)
           • give different shape of orbital
             • s p d f orbitals
         • the magnetic quantum number (ml)
           • give different orientation of orbital
         • the spin quantum number (ms)
           • represent spin of electron. Only two possible values : +1/2 and -1/2
   • Wave Particle Duality
     • In subatomic level, energy and matter cannot be distinguished. They have both light and particle properties.
       • light consists of particles called photon. Photon travels as wave.
       • Matter consists of atom and subatomic particles. Subatomic particles such as electrons travel or move as wave.

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