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Arrangement of electrons in the atom

1. Heisenberg Uncertainty Principal

   • It is impossible to tell the position and velocity of an electron at the same time

2. Bohr

   • * The formation of emision line spectra indicates the presence of energy levels in atoms
   • * An emission line spectra consists of coloured lines against a dark background
   • Bohr's Theory
     • -Proposed that electrons revolve around the nucleus in fixed paths called orbits/ energy levels
     • -Proposed that the energy of an electron in an energy level is fixed at a definate amount

3. * Electrons always occupy the lowest available energy levels.This is known as the ground state

   • * When an element is heated, electrons gain energy and move to higher energy levels. This is the excited state and is only temporary
   • * As an electrons lose energy they return to lower energy levels and emit light in the form of a photon.
   • The energy of the photon is equal to the energy difference between the energy level it fell from and the one it fell into.
     • E2-E1=hF

4. Absorption Spectrum

   • * An absorption spectrum is produced when white light is passed through a gaseous sample of an element
     • * It consists of dark lines against a coloured background

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