Topic 2: Atomic Structure

2.1 The Nuclear Atom

Dalton's atomic structure (1808)

  • All matter consists of atoms

  • Elements consist of atoms

  • Compound consist of atoms of more than one element

  • In a reaction atoms are not created nor destroyed

Thomson's model (1906)

  • "Plum pudding" model

Rutherford's gold foil experiment

  • Proved the empty space in an atom

Sub atomic particles

  • Proton

  • Neutron

  • Electron

Nuclear symbol

A: number of protons + neutrons

Z: number of protons

Mass spectrometer

  • Used to determine the Relative atomic mass of an element

  • 5 StagesVaporization-->ionization--> acceleration-->deflection-->detection

Tip: You only need to know the order of the stages, not how each stage works.

Radio isotopes​​

  • medical chemistry

    • Iodine 131 to obtain image of tyre​oid gland

    • iodine 125 to treat cancer and tumors

    • Cobalt 60 in radiotherapy

  • Dating

    • Carbon 14 in cosmic, geological and archeological dating​

      • Half-Life: time it takes for an amount of radioactive  isotopes to decrease to one half of its initial value​

      • Example: carbon half-life: 5730 years

2.2 Electron Configuration

Emission Spectra

  • A pure gaseous element subjected to a high voltage and reduced pressure will emit a certain wave length.

  • Quantisation energy:

    • formula:

  • When the electron falls back from the excited state to the ground state it emits a photon, a discrete amount of energy.

  • Hydrogen line emission spectrum

  • Series

  • At the limit of convergence of the spectra there is a continuum. Beyond this energy there is a free electron.

Orbitals (Quantum mechanical model)

  • Region in space where there is a high probability of finding an electron

  • each orbital can hold a maximum of 2 electrons

  • s orbital is spherically symmetrical

  • p orbital is dumbbell shaped. There are 3 atomic orbitals,               each in one cartesian axes


    • Orbital diagram:

      • Example:​ Zn

    • ​​​​Condensed configuration:

      • ​​Example:​

  • Configurations​​

    • Full electron configuration:

      • Example​: