Atomic Stucture

Ions
1. Ions have different numbers of protons and electrons
  1. Ions formed by gaining or losing electrons from the atom
    1. Positive ions have lost electrons
      1. Negative ions have gained electrons
        Negative Ions repel
Isotopes
1. Same element with different numbers of neutrons
2. Number and arrangement of electorns decide the chemical properties of an element
  1. Isotopes have the same electrons / config so same chemical porperties
    1. Slightly different physical properties due to different mass of atom
ToF Mass Spectrometer
1. Ionisation
  1. Electron Impact
    1. Sample is vaporised
      1. High energy electrons fired at sample from an electron gun
        Forms +1 ions that are attracted to -ve plate
  2. Electrospray
    1. Sample dissolved in volatile solvent
      1. Injected through fine needle
        Tip of needle attached to +ve end of high-voltage supply
        Forms +1 ions by gaining a proton from solvent
2. Detection
  1. Positive ions discharged
    1. By gaining electrons when hit detector
      1. Generates a current from the movement of electrons
        Size of current indicates number of ions hitting plate
        Mass spectrum
        Data used to produce graph
        mass to charge ratio (m/z) against abundance
        used to work out relative atomic mass of element
        = mass of isotopes / abundance
        Greatest m/z value
        Tells us the relative mass of sample
        small signal may be above it
        this is due to ions having higher mass on a single atom
        Signals below are due to fragmentation of molecular ions
3. Flight Tube
  1. Low mass, faster
    1. Fastest meets detector first
4. Acceleration
  1. +1 ions accelerated using electric field
    1. So that they all have the same kinetic energy
      1. Velocity depends on mass
        low mass, faster
5. Instrumental method of analysis
  1. Used to find abundance and mass of each isotope of an element
    1. This allows us to find its relative atomic mass
    2. Used to find relative molecular mass of substances of molecules
Electronic Structure
1. Electron shells made up of sub-shells and orbitals
  1. Electrons move around nucleus in regions of an atom - shells or energy levels
    1. Shells are divided into sub-shells which have slightly different energies
      1. Sub-shells have different numbers of orbitals which can each hold 2 electrons
        Two electrons in each orbital spin in opposite directions due to repulsion
        1s^2 - 1 orbital, 2e-
        2p^6 - 3 orbitals, 6e-
        3d^10 - 5 orbitals, 10e-
        4f^14 - 7 orbitals, 14e-
2. Further the shell is from the nucleus, the higher its energy
3. Number of outer shell electrons decide chemical properties
  1. Group 1 and 2 easily lose electrons from outershell to from positive ion
    1. Group 5, 6 ,7 can gain 1, 2, 3 electrons form negative ions
      1. Group 4, 7 share electrons to form covalent bonds
        Group 0 have filled sub-shells, dont react making them inert
        Transition metals lose s, d electrons forming positive ions
        Transition metals are unusual
        Copper and Chromium fill their 4s sub shell singly
        Energetically more favourable to fill 3d sub shell first
        They also lose the 4s electron before 3d when becoming ions
    2. Form inert gas configuration
Ionisation Energy
1. Ionisation - removal of electrons from atoms or molecule
2. Factors
  1. Nuclear Charge
    1. more protons in nucleus, stronger the attaction to electrons
  2. Shielding
    1. More electrons between nucleus and outer electron, less attaction between the two
  3. Nucleus Radii
    1. Attraction falls off rapidly with distance, larger the radii, less attaction
3. Trends
  1. Across any period
    1. Increase harder to remove outer electron
      1. Across period increasing nuclear charge, more protons
        Shielding the same across
        More attaction between the electrons and protons
  2. Down a group
    1. Extra electron shells
      1. Less attraction between positive nucleus and outer electron
        Furthest electron far away
  3. ALM
    1. Despite increase in nuclear charge,
      1. Outer Al electron in a higher energy sub-shell
        increase shielding
        Less energy needed to remove the electron
      2. Same shielding, same orbital
        Phosphorus has 1 fully occupied orbital
        Repulsion in the electron orbital
  4. SLP

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Atomic Stucture

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	Erstellt von Dominic Weston vor fast 7 Jahre