Atomic structure

• What are the three sub-atomic particles of an atom?

  Proton, neutron, and electron
• Where is the proton located in an atom?

  In the nucleus
• What is the relative mass of a neutron?

  1
• What is the relative charge of an electron?

  • 1
• What does the atomic number (Z) represent?

  The number of protons in the nucleus
• How is the mass number (A) defined?

  As the total number of protons and neutrons in the atom
• How do you calculate the number of neutrons in an atom?

  By using the formula $Number\ of\ neutrons =$$A - Z$
• What are isotopes?

  Atoms with the same number of protons but different numbers of neutrons
• Why do isotopes have similar chemical properties?

  Because they have the same electronic structure
• What is the purpose of a mass spectrometer?

  To determine all the isotopes present in a sample of an element
• What are the essential steps in a mass spectrometer?

  1. Ionisation
  2. Acceleration
  3. Flight Tube
  4. Detection
• What is the first step in the mass spectrometer process?

  Ionisation
• What happens during electron impact ionisation?

  A vaporised sample is injected and high energy electrons knock out an outer electron
• What is the role of the high voltage in electro spray ionisation?

  It helps the sample molecule gain a proton from the solvent
• Why must the mass spectrometer be under a vacuum?

  To prevent air particles from ionising and registering on the detector
• What happens to positive ions in the acceleration area of the mass spectrometer?

  They are accelerated by an electric field to a constant kinetic energy
• How do lighter and heavier ions behave in the flight tube?

  Lighter ions move faster than heavier ions
• What is detected in the detection area of the mass spectrometer?

  The ions generate a small current proportional to their abundance
• How is the time of flight calculated in a mass spectrometer?

  Using the formula $t =$$\frac{d}{v}$
• What does the mass spectrometer measure for each isotope?

  A mass/charge ratio (m/z) and an abundance
• What is the relative atomic mass (R.A.M) based on?

  A weighted average of all the isotopes
• What is the R.A.M of magnesium given the isotopic data?

  $24.3$
• What is the significance of the molecular ion peak in mass spectrometry?

  It corresponds to the complete molecule and equals the relative molecular mass (Mr)
• What happens to the molecule in electron impact ionisation?

  It often breaks up and gives a series of peaks
• What is the effect of electro spray ionisation on the molecule?

  Fragmentation does not occur
• What is the shape of s and p sublevels?

  s sublevels are spherical, while p sublevels are shaped like dumbbells
• How are electrons arranged in an atom according to the A-level model?

  Electrons are arranged in principal energy levels and sub-levels
• What is the order of filling sub-shells in an atom?

  1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p
• What does a spin diagram represent?

  It shows the different spins of electrons in an orbital
• How does the electronic structure change when forming positive and negative ions?

  Electrons are lost from the outermost shell for positive ions and gained for negative ions
• What is the electronic structure of magnesium (Mg)?

  1s² 2s² 2p⁶ 3s²
• What is the electronic structure of oxygen (O)?

  1s² 2s² 2p⁴
• What is the electronic structure of calcium (Ca)?

  1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
• What is the electronic structure of chromium (Cr)?

  1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
• What is the electronic structure of iron (Fe)?

  1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
• What is the electronic structure of titanium (Ti)?


  1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d²
• What is the electronic structure of vanadium (V)?

  1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d³
• What is the electronic structure of cobalt (Co)?


  1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷
• What are the shapes of the orbitals in an atom?

  • s orbitals: spherical
  • p orbitals: dumbbell-shaped
• What is the significance of the principal energy levels and sub-levels in atomic structure?

  • Principal energy levels: numbered 1, 2, 3, 4...
  • Sub-levels: s, p, d, f with specific electron capacities