atomic structure

• How has the model for atomic structure evolved over time?


  It has changed as knowledge and scientific understanding has improved.
• What is the Plum Pudding Model of atomic structure?


  • Atoms consist of a sphere of positive charge
  • Small negative charges are distributed evenly within it
• What does the Electron Shell Model state about atomic structure?


  • Atoms have a small, dense central nucleus
  • Nucleus is surrounded by orbiting electrons in electron shells
  • Discovered in the Rutherford scattering experiment in 1911
• What particles make up the nucleus of an atom?


  The nucleus consists of protons and neutrons.
• What is the overall charge of the nucleus?


  The nucleus has an overall positive charge.
• What does a neutral atom have in terms of protons and electrons?


  A neutral atom has an equal number of protons and electrons.
• 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?


  It can be calculated using the formula $2n^2$, where $n$ is the shell number.
• How many electrons can shell 2 hold?


  Shell 2 can hold 8 electrons.
• What must happen before the next electron shell can hold electrons?


  Each electron shell must be filled before the next one can hold any electrons.
• What is mass number represented by?


  Mass number is represented by $A$.
• How is mass number calculated?


  Mass number is the sum of protons and neutrons in an atom.
• What does atomic number represent?


  Atomic number is equal to the number of protons in an atom.
• Given an atomic number of 7 and a mass number of 14, how many neutrons are present?


  There are 7 neutrons present.
• What is relative atomic mass defined as?

  Relative atomic mass is the mean mass of an atom of an element divided by one twelfth of the mean mass of an atom of the carbon-12 isotope.

  
• What do isotopes have in common and how do they differ?


  Isotopes have the same atomic number but different numbers of neutrons, resulting in different mass numbers.
• How do neutral atoms of isotopes react chemically?


  They react chemically in the same way as their proton number and electron configuration is the same.
• What is the effect of different mass numbers on isotopes?


  Different mass numbers mean isotopes have different physical properties.
• What are the three isotopes of hydrogen?


  • Hydrogen: 1 proton, 0 neutrons
  • Deuterium: 1 proton, 1 neutron
  • Tritium: 1 proton, 2 neutrons
• What are ions and how are they formed?


  Ions are formed when an atom loses or gains electrons, resulting in an overall charge.
• What is mass spectrometry used for?


  • It identifies different isotopes
  • It finds the overall relative atomic mass of an element
• What are the steps in Time of Flight (TOF) Mass Spectrometry?


  1. Ionisation: Sample is vapourised and ionised
  2. Acceleration: Ions are accelerated towards a detection plate
  3. Ion Drift: Ions are deflected by a magnetic field
  4. Detection: Ions hit the detection plate, producing a flow of charge
  5. Analysis: Current values and flight times produce a spectra print-out
• What happens during the ionisation process in mass spectrometry?


  A sample is vapourised and a high voltage causes electrons to be removed, leaving +1 charged ions.
• What occurs during the acceleration step in mass spectrometry?


  Positively charged ions are accelerated towards a negatively charged detection plate.
• How does the ion drift step work in mass spectrometry?


  The ions are deflected by a magnetic field into a curved path, dependent on their charge and mass.
• What happens during the detection step in mass spectrometry?


  When positive ions hit the detection plate, they gain an electron, producing a flow of charge.
• How is the analysis step conducted in mass spectrometry?

  Current values are combined with flight times to produce a spectra print-out showing relative abundance of each isotope.
• What effect does a 2+ charged ion have on the mass spectrometry results?

  A 2+ charged ion produces a curved path of smaller radius, halving its mass to charge ratio (m/z).
• How is relative atomic mass (Ar) calculated using isotopes?


  Ar = \frac{(10 \times 75) + (12 \times 25)}{75 + 25} =$10.5$
• What is the characteristic pattern of chlorine spectra in mass spectrometry?

  • Cl⁺ ions show a 3:1 ratio
  • Cl₂⁺ ions show a 3:6:9 ratio
  • Reflects the abundance of isotopes and molecular combinations
• What are the types of electron orbitals?


  The types of electron orbitals are s, p, d, and f.
• How many electrons can each type of orbital hold?


  1. orbital = 2, p-orbital = 6, d-orbital = 10.
• In what order are orbitals filled?


  Orbitals are filled in order of increasing energy from s to d.
• What is the electron configuration for sodium (Na) with 11 electrons?


  Na = $1s^2 2s^2 2p^6 3s^1$
• What is the significance of electron spin in orbitals?


  Electrons pair up with opposite spin to achieve stability within an orbital.
• What are the three rules for writing electron configurations?


  1. The lowest energy orbital is filled first.
  2. Electrons with the same spin fill an orbital first before pairing begins.
  3. No single orbital holds more than 2 electrons.
• What happens if electron spins are unpaired in an atom?


  Unpaired spins produce natural repulsion, making the atom unstable.
• How does the electron configuration change for an unstable atom?


  The electron configuration may change to improve stability.
• What is ionisation energy defined as?


  Ionisation energy is 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?


  More energy is usually required to remove successive electrons due to increased attraction to the nucleus.