Structure of Atoms

• Nuclear symbol
• Some elements and their symbols
• Electron shells


  Levels where electrons are grouped, labelled using integers (n) with the closest being labelled 1 and the furthest, if it exists, labelled 7
• Atom


  An individual unit that makes up all matter
• As the metal atoms have been heated to very high temperature, some of their electrons have moved to higher energy levels. As electrons return to lower energy levels in the metal atom, light of a particular wavelength (colour) is emitted
• Energy levels

  Each shell corresponds to an energy level that electrons can occupy, with the first shell having the lowest energy level and the energy level increasing as the shell number increases
• Determine the number of neutrons in the neutral atom

  A - Z = 19 - 9 = 10 neutrons
• Subatomic particles

  • Positively charged protons
  • Neutral neutrons
  • Negatively charged electrons
• Determine the number of electrons in the negative ion

  Z - ionic charge = 7 - (-3) = 10 neutrons
• Electrons


  Located outside the nucleus in defined orbital spaces due to electrostatic forces of attraction between the nucleus and electron cloud
• If an atom were the size of the Woolloongabba cricket ground, then the nucleus would be the size of a pea, and the electrons would be found in a stadium-sized cloud
• Each energy level can hold a particular number of electrons, determined by the formula 2n^2, allowing for the determination of the electron configuration of any atom as each shell can only contain a maximum number of electrons
• Properties of subatomic particles


  • Particle: Proton, Symbol: p, Mass (Kg): 1.673 x 10^-27, Relative mass to a proton: 1, Charge (C): +1
  • Particle: Neutron, Symbol: n, Mass (Kg): 1.6775 x 10^-27, Relative mass to a proton: 1, Charge (C): 0
  • Particle: Electron, Symbol: e, Mass (Kg): 9.109 x 10^-31, Relative mass to a proton: 1/1800, Charge (C): -1
• Aufbau principle states that electrons will occupy lower energy orbitals in higher energy levels than occupy energy levels in sequential order
• Maximum number in a shell is 2n^2
• Energy sublevels


  Each sublevel within an energy level has its own number of orbitals and distinct orbital shapes
• The order of filling electrons into shells and subshells is from the lowest energy as first described by the Aufbau principle
• Pauli Exclusion principle states that an orbital can contain 2 electrons at any one time, but in opposing directions
• Shells are numbered from 1 to 7 corresponding to the period number
• It is possible to determine the electron configuration of any atom as each shell can only contain a max number of electrons
• Subshells s, p, d, f are within these shells with each having a maximum number of electrons they can hold
• Chromium and copper are the only exceptions to the electron configuration model
• s orbitals are spherical, p orbitals are dumbbell-shaped, most d orbitals are cloverleaf-shaped, and f orbitals are varied in shape
• Quantum mechanical model


  The model that explains all experimental findings is referred to as the Quantum mechanical model
• Electron shell (n) and Maximum number of electrons

  • 1 - 2
  • 2 - 8
  • 3 - 18
  • 4 - 32
• Each shell or energy level can hold a particular number of electrons determined by the formula 2n^2
• Sublevels and Maximum number of electrons

  • s - 2
  • s, p - 8
  • s, p, d - 18
  • s, p, d, f - 32
• Rules for creating orbital diagrams

  • Aufbau principle
  • Pauli Exclusion principle
  • Hund's Rule
• The sum of the superscripts in electron configurations equals the atomic number of the element
• Electron Orbitals


  • 1s
  • 2s
  • 2p
  • 3s
  • 3p
  • 4s
  • 3d
  • 4p
  • 5s
  • 4d
  • 5p
  • 4f
  • 6s
  • 5d
  • 6p
  • 5f
  • 7s
  • 6d
  • 7p
• Answers 2.3
• Exceptional electron Configurations occur when half-filled sublevels are more stable than other configurations due to subtle electron-electron interactions in orbitals with similar energies (e.g., 5f and 6d, and 3d and 4s orbitals)
• Check Questions 2.3 / Chapter review 2
• Check Questions 2.4
• Writing Electron Configurations

  First, determine how many electrons are in the atom. Arrange the energy sublevels according to increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc. Fill each sublevel with electrons until you have used all the electrons in the atom.
• Answers 2.4
• Historical development of the atomic model

  Activity: Listen intently and record as much information as you can. Specifically name the scientist and the basic principles of their theory. Link: https://www.youtube.com/watch?v=vUzTQWn-wfE
• Pauli Exclusion principle states that an orbital can contain 2 electrons at any one time, but in opposing directions. This is indicated with oppositely pointed arrows to show one electron in a clockwise direction and another in an anticlockwise direction.
• Chapter 2 Review
• Hund’s rule states that when electrons occupy orbitals of equal energy (e.g., p has 3 orbitals), then one upwards pointing electron must be entered into each of the orbitals before a second electron can enter any of the orbitals.