atomic structure

atomic structure

1. the nuclear atom

   • 92 naturally occurring elements
   • atoms
     • electrons
       • negatively charged
       • orbit around the nucleus
     • nucleus
       • protons
         • positively charged
         • atomic number
           • the number of protons in the nucleus
             • = the number of electrons
           • Z
       • neutrons
         • neutrally charged
         • = mass number - atomic number
       • mass number
         • the number of protons plus neutrons in the nucleus of an atom
         • A
   • ions
     • charged particles that are formed then an atom loses or gains electrons
     • anion
       • negatively charged ion
       • gains electrons
     • cation
       • positively charged ion
       • loses electrons
   • isotopes
     • different atoms of the same element with different mass numbers
       • different number of neutrons
     • the same chemical properties
       • but different physical properties
         • like melting points
   • relative atomic mass
     • the average of the masses of the isotopes in a naturally occurring sample relative to the mass of 1/12 of an atom of carbon-12
     • mass specrtometer
       • vaporisation
         • ionization
           • acceleration
             • deflection
               • detection

2. electron configuration

   • energy level
     • shell
     • increase energy as they get closer to the nucleus
     • principal quantum number
       • 2n^2
   • electromagnetic spectrum
     • frequency is proportional to the energy
     • frequency is opposite to the wavelength
     • emission spectrum
       • each element has its own unique emission spectrum
       • light
     • line spectrum
       • only certain frequencies/wavelengths of light present
     • continuous spectrum
       • all frequencies/wavelengths of light present
     • passing an electric discharge through a gas causes an electron to be promoted to a higher energy shell
       • the electron is unstable in this higher energy shell
         • the electron will fall to a lower energy level
           • as it returns the extra energy is given out
             • energy of higher shell - energy of lower shell
             • in the form of a photon of light
             • this contributes to a line in the spectrum
               • the different series of lines occur when electrons fall back down to different energy level
                 • Paschen series
                   • infrared
                 • Balmer series
                   • visible
                 • Lyman series
                   • ultraviolet
     • convergence
       • the lines in emission spectrum get closer together at higher frequency
       • convergence limit
         • the lines merge to forma continuum
     • sub-energy levels
       • each main energy level in an atom is made up of them
   • the Aufbau principle
     • electrons fill sub-levels from the lowest energy level upwards
   • orbital
     • s
       • p
         • d
           • f
     • a region of space in which there is a high probability of finding an electron
     • represents a discrete energy level
     • Pauli exclusion principle
       • the maximum number of electrons in an orbital is two
       • electrons in one orbital must have opposite spin
     • Hund's rule
       • electrons fill orbitals of the same energy
         • so as to give the maximum number of electrons with the same spin
     • EXCEPTIONS
       • have only one electron in the 4s sub-level
       • chromium
       • copper

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