Atomic Structure-NOTES

• 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?

  Protons and neutrons
• What is the overall charge of the nucleus?

  The nucleus has an overall positive charge.
• What is the relationship between protons and electrons in a neutral atom?

  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 shell number.
• How many electrons can shell 2 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 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
• How is relative atomic mass (Ar) defined?

  Mean mass of an atom of an element divided by one twelfth of the mean mass of carbon-12.

  
• What are isotopes?

  • Atoms of the same element
  • Same atomic number but different number of neutrons
  • Result in different mass numbers
• How do neutral atoms of isotopes behave chemically?

  They react chemically in the same way due to the same proton number and electron configuration.
• What physical properties differ among isotopes?

  They have different mass numbers, leading to different physical properties.
• What are the examples of isotopes of hydrogen?

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

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

  • Identify different isotopes
  • Find the overall relative atomic mass of an element
• What are the steps in 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 process in mass spectrometry?

  A high voltage causes electrons to be removed from atoms, creating +1 charged ions.
• How are ions accelerated in mass spectrometry?

  Positively charged ions are accelerated towards a negatively charged detection plate.
• What determines the radius of the ion's path in mass spectrometry?

  The radius is dependent on the charge and mass of the ion.
• What occurs during the detection phase of mass spectrometry?

  Positive ions hit the detection plate, gain an electron, and produce a flow of charge.
• How is the relative abundance of each isotope displayed in mass spectrometry?

  Current values and flight times are used to produce a spectra print-out.
• What happens if a 2+ charged ion is produced during ionisation?

  It will have a smaller radius path due to being affected more by the magnetic field.
• How can the relative atomic mass (Ar) be calculated using mass spectrometry data?

  Using the formula \(Ar = \frac{(10 \times 75) + (12 \times 25)}{(75 + 25)}\).

  
• What does the chlorine spectra produced by mass spectrometry show?

  • Characteristic pattern in a 3:1 ratio for Cl⁺ ions
  • 3:6:9 ratio for Cl₂⁺ ions
  • Indicates one isotope is more common than the other

  
• What are the isotopes of chlorine that can be detected in mass spectrometry?

  Cl₂⁺ can be 70Cl₂⁺, 72Cl₂⁺, or 74Cl₂⁺.

  
• What are the types of electron orbitals and their electron capacities?

  • s-orbital: 2 electrons
  • p-orbital: 6 electrons
  • d-orbital: 10 electrons

  
• How does the energy of orbitals change in relation to their type?

  The energy of the orbitals increases from s to d.
• What is the electron configuration for sodium (Na) with 11 electrons?

  Na = 1s²2s²2p⁶3s¹
• 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 and unbalanced?

  It produces natural repulsion between electrons, making the atom unstable.
• How does the electron configuration change for an unstable atom?

  Electrons may take on a different arrangement to improve stability.
• 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 due to increased electrostatic attraction.

  
• What are the trends in first ionisation energy across a period and down a group in the Periodic Table?

  • Across a Period: First ionisation energy increases due to decreasing atomic radius and greater attraction.
  • Down a Group: First ionisation energy decreases due to increasing atomic radius and shielding.
• What indicates a change in energy level when plotting successive ionisation energies on a graph?

  A sudden large increase in energy indicates an electron is being removed from an orbital closer to the nucleus.