Atomic structure

Sub-atomic particles
1. Electrons
  1. Charge- -1
  2. Mass- Neglidgible
  3. no. of electrons in shell = 2n^2
2. Nucleons
  1. Protons
    1. Mass- 1
    2. Charge- +1
  2. Neutrons
    1. Charge- 0
    2. Mass- 1
Atoms
1. Mass no.- protons+neutrons
2. Atomic no.- protons
3. Isotope- Same no. of protons, different no. of neutrons
Mass spectroscopy
1. Vacuum so that ions do not collide with air molecules
2. Gaseous sample
3. Ionisation
  1. Beam of electrons knocks out an electron (+ion formed)
    1. Sometimes 2 elections knocked out (halves the m/z)
4. Acceleration
  1. Positive ions attracted to negatively charged plates
    1. The speed they go depends on the mass
      1. Some pass through slits in the plate, forming an ion beam
5. Deflection
  1. Beam of ions move into magnetic field at right angles to its direction of travel
    1. Magnetic field deflects the ions into an arc of a circle
  2. Deflection depends on
    1. m/z ratio
    2. 2+ ions deflected twice as much as 1+ ions with the same mass
    3. EMF strength
6. Detection
  1. EMF gradually increased so ions of increasing mass enter the detector
    1. Ions accept electrons when they strike the detector, so lose charge
      1. creates a current that is proportional to the abundance of each ion
7. Results
  1. From the strength of the EMF at which an ion hits the detector, a computer works out the m/z ratio of the original ion
    1. Mass spectrum produced
      1. Isotopes
        Average relative atomic mass = Σ(abundance x m/z) ÷ overall abundance
      2. Molecular ions e.g. Cl2
Electron arrangement
1. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10 4f14
  1. Add 4s before 3d
  2. Remove 4s before 3d
  3. When a full orbital, electron spin =0
  4. When in a new sub level, each orbital is singly filled before being doubly filled
Electron arrangement and ionisation energy
1. The energy required to remove one mole of electrons from one mole of gaseous atoms
  1. Each ionisation requires more energy than the prior one (successive ionisation energies)
    1. Depending on how close each ionisation energy is, it shows how many electrons are in a shell

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	Criado por Chemistry quase 11 anos atrás