Atomic Structure

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  • Atomic Structure
    • The Atom
      • All elements are made up of atoms.
      • Atoms are made up of protons and neutrons in the  nucleus, and electrons orbiting the nucleus.
        • Protons have a mass of 1 and a charge of +1.
        • Neutrons have a mass of 1 and a charge of 0.
        • Electrons have a mass of 0 and a charge of -1.
      • In neutral atoms there is the same number of protons and electrons.
      • Ions are charged particles that have either lost or gained electrons.
      • Isotopes of an element are atoms with a different number of neutrons.
    • Atomic Models
      • Dalton and Thomson's model (the plum pudding) suggested that protons were large, solid, positive particle with small negatively charged particles inside.
      • Rutherford's model suggested that an atom is a positively charged nucleus surrounded by smaller negatively charged particles.
        • Rutherford disproved the 'plum pudding' via the gold foil experiment.
      • Bohr's model   is similar to Rutherford's model however suggests that electrons are found in fixed energy levels.
    • Relative Mass
      • Relative atomic mass is the average mass of an atom of an element on a scale where an atom of C12 is exactly 12.
      • Relative isotopic mass is the average mass of an isotope of an element on a scale where an atom of C12 is exactly 12.
      • Relative molecular mass is the average mass of a molecule on a scale where an atom of C12 is exactly 12.
      • Relative formula mass is the average mass of a formula unit on a scale where an atom of C12 is exactly 12.
    • Mass Spectrometry
      • Mass spectrometers can tell you relative atomic mass, relative molecular mass relative isotopic abundance and molecular structure.
        • 1. Vaporisation - the sample is turned into a gas.
        • 2. Ionisation -  The gas particles are bombarded by electron which knock electrons off the particles leaving positively charged ions.
        • 3. Acceleration -  The ions are accelerated by an electric field.
        • 4. Deflection -  Lighter ions are deflected by a magnetic field as they have less momentum so only ions with a specific mass/charge ratio are detected.
        • 5. Detection  - As ions hit the detector a current flows which produces a mass spectrum.
      • A mass spectrum has  abundance on the y axis and mass/charge on the x axis.
    • Electronic Structure
      • Electrons are found in orbitals, within sub shells, within energy levels.
      • Different energy levels contain different sub shells.
        • The 1st  energy level contains a 1s sub shell.
        • The 2nd  energy level contains a 2s and 2p sub shell.
        • The 3rd  energy level contains a 3s, 3p and 3d sub shell.
        • The 4th  energy level contains a 4s, 4p, 4d and 4f sub shell.
      • Energy level diagrams and sub-shell notations are used to represent electronic structure.
      • There are rules to electron structure.
        • Electrons fill lowest energy sub shells first.
        • Electrons fill orbitals singularly before sharing.
        • When electrons are lost, they are lost from the highest possible energy level.
        • Cu and Cr rather have a half or full 3d then a full 4s.
        • 4s sub shell is filled before 3d.
    • Ionisation Energies
      • The first ionisation energy is the energy needed to remove 1 electron form each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
      • There are 3 main factors that affect ionisation energy.
        • Nuclear Charge - the higher the positive charge in the nucleus the greater the pull (so ionisation energy increases).
        • Distance from nucleus - The greater the distance the less attraction between the nucleus and outer electron (so ionisation energy decreases).
        • Shielding - the greater the number of electrons between the nucleus and outer electron the smaller the attraction (so ionisation energy decreases0.
      • Down group 2 ionisation energy decreases as shielding and distance increases.
      • Ionisation energy increases across a period as nuclear charge increases however decreases slightly as a new sub shell starts to fill.


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