Atomic Structure

• What are the trends in ionisation energy for down a group?

  • Decreases down the group
  • Due to increased atomic radius and shielding
• What are the trends in ionisation energy across a period?

  • Increases across the period
  • Due to increased nuclear charge
  • Shielding remains similar
• Why was the atomic model refined to include subshells?

  Not all electrons in the same shell have the same energy
• What is relative atomic mass?

  Average mass of an atom of an element compared to the mass of one atom of carbon-12
• What is relative isotopic mass?

  Mass of an atom of an isotope compared to the mass of one atom of carbon-12
• What is relative molecular mass?

  Average mass of a molecule compared to the mass of one atom of carbon-12
• How do isotopes compare chemically?

  They have the same chemical properties due to same electron configuration
• What physical properties differ among isotopes?

  Density and mass
• How does TOFMS separate ions?

  By charge-to-mass ratio
• What is electron impact ionisation used for?

  Compounds with low molecular mass
• What does data analysis in TOFMS generate?

  A mass spectrum
• What does a mass spectrum show?

  Mass:charge ratio and relative % abundance
• How can mass spectra be used to identify elements?

  Each isotope produces a line on the spectra
• What does the main peak in mass spectra represent?

  Relative molecular mass
• What happens during fragmentation in mass spectrometry?

  Molecular ions break into smaller particles
• What is the first step in determining the electron configuration of elements?

  Fill the lowest energy subshells first
• What is the order of filling subshells according to the Aufbau principle?

  1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d...
• What is Hund's rule in electron configuration?

  Electrons fill orbitals singly before pairing
• What happens to the highest energy levels when losing electrons?

  They are lost first
• What causes the dip in ionisation energy between groups 2 and 3?

  Move to a new energy level with higher energy
• What causes the dip in ionisation energy between groups 5 and 6?

  Electrons in the same orbital repel each other
• What does successive ionisation energy refer to?

  Removing more electrons from an increasingly positive ion
• What happens to ionisation energy when breaking into a new shell?

  There is a sudden rise in ionisation energy
• What is evidence for shell structure in ionisation energy?

  Sudden jumps in ionisation energy indicate new shells
• What does a drop in ionisation energy between groups 2 and 3 indicate?

  Evidence for subshells in electron configuration
• What is the structure of an atom?

  Consists of a nucleus containing protons and neutrons surrounded by electrons in energy levels
• What relative charge and mass does a proton have?

  +1 charge, 1 atomic mass unit
• What relative charge and mass does a neutron have?

  0 neutral charge, 1 atomic mass unit
• What relative charge and mass does an electron have?

  -1 charge, 1/2000 atomic mass unit
• What does the mass number [A] represent?


  Number of protons and neutrons in the nucleus
• What does the atomic number [Z] indicate?



  Number of protons in the nucleus
• How does the atomic number relate to electrons?

  It equals the number of electrons in a neutral atom
• What was Dalton's proposal on the atomic model?

  Atoms were solid spheres that make up elements, different spheres for each element
• What was Thomson's proposal on the atomic model?


  Plum pudding model showing atoms contain electrons
• What was Rutherford's proposal on the atomic model?


  Most of atom is empty space with a small positive nucleus at centre
• What was Bohr's proposal on the atomic model?


  Electrons are in shells/orbitals of fixed energy
• Define an isotope

  An atom of the same element with the same number of protons but different number of neutrons (different mass number)
• What does the mass spectrometer give accurate information on?

  Relative isotopic mass and relative abundance of isotopes
• What is the mass spectrometer used for?

  Work out relative atomic masses to identify elements + determine relative molecular masses
• Why does a mass spectrometer need to be under a vacuum?

  Prevent air molecules to ionise and register on the detector