atomic structure & PT

• What has caused the model for atomic structure to evolve over time?

  Changes in knowledge and scientific understanding
• What does the current accepted model of the atom consist of?

  A small, dense central nucleus surrounded by orbiting electrons in electron shells

  
• In what year was the Rutherford scattering experiment conducted?

  1911
• What particles make up the nucleus of an atom?

  Protons and neutrons
• What charge does the nucleus of an atom have?

  Overall positive charge
• What does a neutral atom have in terms of protons and electrons?

  The number of electrons is equal to the number of protons
• What are the relative charges and masses of protons, neutrons, and electrons?

  • Proton: Charge +1, Mass 1
  • Neutron: Charge 0, Mass 1
  • Electron: Charge -1, Mass 1/1840
• How can the maximum number of orbiting electrons in a shell be calculated?


  Using the formula \(2n^2\) where \(n\) is the number of the shell
• How many electrons can shell 2 hold?

  8 electrons
• What must happen before the next electron shell can hold electrons?

  Each electron shell must fill
• What does the mass number (A) represent?

  The sum of protons and neutrons in an atom
• What does the atomic number (Z) represent?

  The number of protons in an atom
• If an atom has an atomic number of 7 and a mass number of 14, how many neutrons does it have?

  7 neutrons
• What are isotopes?

  • Atoms of the same element
  • Same atomic number
  • Different number of neutrons
  • Different mass number
• How do neutral atoms of isotopes react chemically?

  They react chemically in the same way
• What affects the physical properties of isotopes?

  The different mass numbers
• What is relative atomic mass (Ar)?

  • Mean mass of an atom of an element
  • Relative to one twelfth of the mean mass of a carbon-12 atom
  • Takes relative abundances of isotopes into account

  
• What is relative isotopic mass?

  • Isotopic mass of an isotope
  • Relative to one twelfth of the mean mass of a carbon-12 atom

  
• What is relative molecular mass (Mr)?

  • Mean mass of a molecule of a compound
  • Relative to one twelfth of the mean mass of a carbon-12 atom
  • Calculated by adding Ar values of component elements

  
• What is relative formula mass?

  • Similar to Mr
  • Used for compounds with giant structures
• How are ions formed?

  When an atom loses or gains electrons
• What analytical technique uses ions?

  Mass spectrometry
• What does mass spectrometry identify?

  Different isotopes and the overall relative atomic mass of an element
• What are the steps of Time of Flight (TOF) Mass Spectrometry?

  1. Ionisation: Sample vapourised and ionised
  2. Acceleration: Ions accelerated towards detection plate
  3. Ion Drift: Ions deflected by magnetic field
  4. Detection: Ions hit detection plate, producing charge
  5. Analysis: Current values and flight times produce spectra

  
• What happens during the ionisation step of TOF Mass Spectrometry?

  A sample is vapourised and ionised, producing +1 charged ions
• What is the effect of a 2+ charged ion in the magnetic field during ion drift?

  It produces a curved path of smaller radius
• How is the relative atomic mass (Ar) calculated from the spectra?

  By multiplying each m/z value by its abundance and dividing by the total abundance
• What does the tallest peak on a mass spectrum correspond to?

  The relative molecular mass of the molecule
• What is the characteristic pattern of chlorine spectra in mass spectrometry?

  • 3:1 ratio for Cl⁺ ions
  • 3:6:9 ratio for Cl₂⁺ ions
• What is ionisation energy defined as?

  The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state
• What happens to ionisation energy as successive electrons are removed?

  It usually requires more energy
• What trend occurs in first ionisation energy along a period in the Periodic Table?

  It increases due to decreasing atomic radius and greater electrostatic forces of attraction

  
• What trend occurs in first ionisation energy down a group in the Periodic Table?

  It decreases due to increasing atomic radius and electron shielding
• What does a sudden large increase in successive ionisation energies indicate?

  A change in energy level
• Why is the first ionisation energy of Aluminium lower than expected?

  Due to a single pair of electrons with opposite spin causing natural repulsion
• What evidence supports the current model of electronic configurations?

  1. Emission spectra provide evidence for quantum shells
  2. Successive ionisation energies suggest group affiliation
  3. First ionisation energy provides evidence for electron subshells

  
• What are electron orbitals?

  • Clouds of negative charge
  • Types: s, p, d, f
  • Each can hold up to two electrons with opposite spins
• How do orbitals correspond with the Periodic Table?

  • Each block on the Periodic Table corresponds to a type of orbital
  • Elements in the block have outer electrons in that orbital
• What is the capacity of each subshell in terms of orbitals and electrons?

  • Each subshell has a different number of orbitals
  • Each orbital can hold 2 electrons
• What is the current accepted model of atomic structure based on?

  It is based on evidence from emission spectra, successive ionisation energies, and first ionisation energy.