Atomic Structure

Atomic Structure

1. The atom

   • elements: the simplest form components of chemistry
     • atoms: the smallest unit of an element
     • There are approximately 92 different types of naturally ocuring elements
   • John Dalton
     • ll matter is composed of tiny indestructable particles called atoms
     • atoms cannot be created nor destroyed
     • Atoms of different elements are different
     • Atoms can combine together in small numbers to form molecules
   • Atoms can react together to form compounds
   • Sub atomic particle
     • Electron: -
       • Ions
         • Anions: gain an electron
         • Cations: lose an electron
     • Nucleus
       • Proton: +
       • Neutron: 0
   • Atomic number and mass number
     • mass number on top
     • Atomic number at the bottom
     • symbol of element in between
   • Isotopes: Atoms of the same element with different numbers of neutrons
     • Radioisotopes
       • generate energy in nuclear power stations
       • sterilize surgical instruments in hospitals
       • preserve food
       • fight crime
       • detect cracks in structural materials
       • Carbon - 14 dating
         • when organisms die, their age can be determined by measuring its rate of decay by determining its half life, the time it takes for half its atoms to decay
       • Cobalt - 60 radio therapy
         • Treatment of cancer and other diseases with ionizing radiation
       • Iodine - 131 medical tracer
         • used to detect radiation levels in ones body however, excessive use could also be harmful

2. The mass spectrometer

   • Vaporization: vaporization of injected sample
   • Ionization: the atoms are made positive through bombardment of high energy electrons
   • Acceleration: the positive ions are attracted to negatively charged plates and are accelerate by an electric field
   • Deflection: the accelerated positive ions are deflected by a magnetic field and the amount of deflection is proportional to the charge/ mass ratio
   • Detection: positive ions of particular mass/ charge ratio are detected and signals are sent to a recorder, the strength of the signals are a measure of the number of ions present with that particular charge/ mass ratio
     • Mass spectrum

3. Electron arrangement

   • Wavelengths
   • Frequency
   • continuous spectrum: made by white light when passed through a prism
   • white light passing through hydrogen gas = absorption spectrum, a line spectrum where only some colors are present. If a high voltage is applied to the gas, a corresponding emission line spectrum is produced
   • Atoms
     • Excited state = high energy level
       • when an atoms goes down energy levels it releases energy in the form of electromagnetic radiation
     • Ground state = low energy level
   • ionization energy: amount of energy required to remove an electron from the ground state in one mol of gaseous atoms
   • Valence electrons = electrons found in the outer most energy level of an atom