1.1 Atomic Structure

• Ion: Different numbers of electrons and protons
• Isotope


  Element with the same number of protons but a different number of neutrons
• Blocks in the periodic table

  • P block
  • D block
  • F block
• Time of flight mass spectrometry


  1. Under a vacuum to prevent air particles from ionising and registering on the detector

  2. Electrospray ionisation: Dissolve the sample in a polar solvent, Push it through a tiny nozzle at high pressure, Apply a high voltage. Each particle will gain a proton and the sample will be a gaseous sample of positive ions

  3. Electron impact ionisation: Vaporise the sample then the sample is bombarded by high energy electrons. An electron will be removed from each particle. This will create +1 ions

  4. Acceleration: The positive ions move through a negative electric field, accelerating toward the negative plate. Particles with lower m/z accelerate more quickly

  5. Ion drift: Particles travel through with constant speed and kinetic energy. Particles with Lower m/z travel faster

  6. Detection: Lighter ions will reach the detector first. When these positive ions hit the detection plate, they gain an electron, producing an electric current. The greater the abundance, the greater the current produced
• Electrospray ionisation over electron impact

  Electron impact can cause larger, organic molecules to fragment. Hence, we use electrospray ionisation for larger, organic molecules - the ''softer'' conditions of this technique mean fragmentation won't occur
• Relative Molecular Mass

  The average mass of a molecule relative to one twelfth of the mass of an atom of carbon-12
• Relative Atomic Mass

  The average mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12
• Relative Isotopic Mass

  The mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12
• Molecular ion on a mass spectra is the last peak on the spectra
• Electron configuration of Ions work

  Add or remove electron from highest energy level first e.g. lose from 4p orbital
• Electron configuration of transition Metals work

  1. Chromium and copper behave differently

  2. Cr(+2) [Ar] 3d⁵ 4s¹: Electron moves from the 4s orbital and moves into the 3d orbital to make a more stable half full 3d sub shell respectively
• First ionisation energy


  The energy required to remove one electron from each of a mole of free gaseous atoms of that element
• Factors affecting ionisation energy

  • The attraction of the nucleus (more protons in the nucleus, means greater attraction)
  • The distance of the electrons from the nucleus (the bigger the atom, the further the outer electrons are from the nucleus and the weaker the attractive force)
  • Shielding of the Attraction from the Nucleus (a greater number of electrons in inner shells will repel those in the outer shell, weakening the attractive force)
• Nucleus

  Greater attraction
• Distance of electrons from the nucleus

  The bigger the atom, the further the outer electrons are from the nucleus and the weaker the attractive force
• Shielding of the Attraction from the Nucleus

  A greater number of electrons in inner shells will repel those in the outer shell, weakening the attraction of the nucleus
• Increase in first ionisation energy across a period

  Electrons are added to the same shell which has the same distance from the nucleus and the same shielding effect. The number of protons increases, making the effective attraction of the nucleus greater
• Trend in first ionisation energies across period 2

  1. General increase across the period as the nuclear charge increases and the shielding remains the same

  2. Drop from Be to B because in B a 2p electron is being removed and the extra shielding from the 2s subshell causes a fall in the effective nuclear charge

  3. Drop from N to O because the electron in O is being removed from a paired orbital, making them less stable and easier to remove
• First ionisation energies decrease down a group


  Outer electrons are found in shells further from the nucleus and are more shielded, so the attraction of the nucleus becomes smaller
• Successive ionisation energies

  1. The second ionisation energy is the energy needed to remove 1 electron from each ion of an element in 1 mole of gaseous +1 ions to form 1 mole of gaseous ions with a +2 charge

  2. Successive ionisation energies are always larger as the positive ion formed increases the attraction on the remaining electrons
• Successive ionisation energies of an atom

  • Always increase as more electrons are removed, resulting in fewer electrons that remain and less repulsion between them, making the electrons more stable and harder to remove
  • The largest jumps between successive ionisation energies come when the electron is removed from an inner shell, causing a large drop in shielding, a large increase in effective nuclear charge, and a large increase in ionisation energy