C1 atomic structure

Cards (40)

  • the sub-atomic particles are protons and neutrons in the nucleus, and electrons orbiting in energy shells
  • relative masses of sub-atomic particles:
    electron = 1/1840
    proton = 1
    neutron = 1
  • relative charges of sub-atomic particles:
    electron = -1
    proton = +1
    neutron = 0
  • atomic number is the number of protons in the nucleus of an atom
  • atomic number is represented by Z
  • mass number is the number of protons and neutrons in the nucleus of an atom
  • mass number is represented by A
  • isotopes are two atoms with the same number of protons and electrons but a different number of neutrons
  • isotopes react in the exact same way chemically
  • electrons orbit the nucleus of an atom and are held in electron shells which increase in energy the further you get from the nucleus
  • electrons can behave as a particle, wave or cloud of charge
  • the first shell holds up to 2 electrons, the second shell holds up to 8 electrons and the third shell holds up to 18 electrons
  • a mass spectrometer is an instrument which can be used to determine the relative atomic mass of a sample
  • there are many types of mass spectrometry but all are based on forming ions and separating the ions based on their charge:mass ratio
  • time-of-flight spectrometry records the time taken for ions to reach a detector and uses this to identify them
  • TOF spectrometry has the following stages:
    • ionisation
    • acceleration
    • ion drift
    • detection
    • analysis
  • in the first stage of TOF spectrometry, ionisation, the sample is vaporised and injected into the chamber
  • the two types of ionisation in TOF spectrometry are electron bombardment, where ions lose an electron, and electrospray, where ions gain a proton, both create 1+ ions
  • in the second stage of TOF spectrometry, acceleration, the molecules are given energy so they all have the same kinetic energy, then accelerated towards a negative plate
  • in the third stage of TOF spectrometry, ion drift, ions are deflected by a magnetic field so travel in a curved path, depending on their charge and mass
  • in the fourth stage of TOF spectrometry, detection, positive ions hit negative plate, they gain an electron, this causes a current to flow, greater abundance = greater current
  • in the fifth stage of TOF spectrometry, analysis, current values are used in combination with flight times to produce a mass spectrum
  • mass spectra are produced from a mass spectrometer, they show the abundance of different ions separated by their mass/charge ratio
  • energy levels are divided into sub-levels, named s, p, d and f
  • different orbitals have different energies depending on the energy level they are in
  • the atomic orbitals of each main level have different shapes with different energies, these are the sub-levels, they represent a volume of space where there is a 95% chance of finding an electron
  • s-orbitals can hold up to 2 electrons
  • p-orbitals can hold up to 2 electrons each, but come in groups of 3 so 6 electrons in the sub-level
  • d-orbitals can hold up to 2 electrons each, but come in groups of 5 so 10 electrons in the sub-level
  • electron configuration is written in the form 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 and so on
  • the 4s orbital is filled before the 3d orbital because it is of lower energy
  • the electron configuration of chromium is 1s2 2s2 2p6 3s2 3p6 4s1 3d5
  • ionisation energy is the minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state
  • first IE is shown by the equation:
    M(g)M+M_{(g)} → M^+(g)+_{(g)} +e e^-
  • second IE is shown by the equation:
    M+M^+(g)M(g)2++_{(g)} → M^{2+}_{(g)} +e e^-
  • third IE is shown by the equation:
    M(g)2+M(g)3++M^{2+}_{(g)} → M^{3+}_{(g)} +e e^-
  • along a period, first IE increases due to decreasing atomic radius and increasing electrostatic forces of attraction
  • down a group, first IE decreases due to increasing shielding and increasing atomic radius
  • electrospray ionisation of X process:
    • X is dissolved in a solvent
    • X is injected through a needle at high voltage
    • it gains a proton
    • the equation is X + H+ -> XH+
  • remember which type of ionisation is which because electrospray ionisation has a p in it so a proton is gained, and electron bombardment has an e in it so an electron is lost
    electron bombardment is the same as electron impact