✔️1 - Atomic structure

• Isotopes have the same number of protons and electrons, but different numbers of neutrons.

  They all react chemically in the same way due to having the same electron configuration.
• A mass spectrometer is used to accurately determine relative atomic masses.
• In a TOF mass spectrometer:

  • The sample is ionised to +1 - either electrospray or electron impact/gun
  • The positive ions are accelerated towards a negatively charged plate. Lighter and more highly charged ions travel faster
  • Ion drift - the ions pass through a hole in the negatively charged plate forming a beam that travels along the flight tube
  • Detection - lighter ions arrive at the detector first and flight times are recorded. The ions pick up an electron from the detector, causing a current

  The signal is then used to generate a mass spectrum.
• Electrospray ionisation - the sample is dissolved in a volatile solvent and forced through a fine needle connected to a high voltage. This causes the the sample to gain a proton.

  Electron impact - the sample is vapourised and high energy electrons are fired at it, knocking off an electron from each particle

  X(g) + e- --> X+(g) + 2e-
• An electron orbital is a cloud where there is a 95% chance of finding an electron.
• S orbitals hold 2 electrons

  P orbitals hold 2 and the sub level totals to 6

  D orbitals hold 2 and the sub level totals to 10
• The 4s sub level is lower energy than the 3d sub level so generally gets filled first.
• The order of orbitals goes s p d f.
• Atomic orbitals of the same energy fill singly before pairing because electrons repel each other.
• Ionisation energy is the energy required to remove a mole of electrons from a mole of atoms in the gaseous state.

  It is measured in kJ mol-1
• Successive ionisation energies get larger as you remove them from 1+ then 2+ ions and so on.
• For ionisation energies, repulsion between electron pairs in orbitals makes them easier to remove.