Atomic Structure

Module Aims

Module Aims

FOUNDATION CHEMISTRY

The first module you will take aims to give you an understanding of the basic concepts of chemistry which will be built on in further modules to give you more specific knowledge of the subject. This module combines elements of basic chemistry and physics to provide you an overview of the science as a whole. By the end of the module you will be equipped with the necessary tools to tackle problems in other areas of chemistry, therefore It is important that you have a good understanding of all of these topics otherwise you will face problems in later modules when this knowledge is assumed.

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The Topics

Atomic Structure:

  1. You should have a clear understanding of the fundamental particles (Protons, Neutrons and Electrons) and be able to give their mass and charges.
  2. The model of atomic structure suggests that atoms and ions with the same arrangements as Noble gasses should be stable.
  3. You should understand that there are a number of models of proton and electron structure.
  4. You need to know the meaning of the mass number (A) and the atomic number (Z). You should also know which is which when read off the periodic table!
  5. You should be able to explain the existence of isotopes and know their natural abundance can have practical applications such as carbon dating.
  6. You need an understanding of how a mass spectrometer works as this is an important analytical tool. Your understanding should be able to explain what is happening at each of the stages of ionisation, acceleration, deflection and detection.
  7. The mass spectrometer is such a useful tool as it gives accurate information on relative isotopic mass and the relative abundance of isotopes. It is therefore very helpful in identifying elements and compounds.
  8. You should be able to use simple mass spectra to calculate relative molecule mass from isotopic abundance (this will be limited to mononuclear ions in the exam so you will not be given anything too complicated).
  9. You need to be able to give the electron configuration of atoms and ions up to Z=36 in terns of s, p and d orbitals.
  10. You should also learn how to draw the s,p and d orbitals- be careful when you label your x, y and z axis so you’re giving the orbitals the right orientation.
  11. You need to be able to define the ‘ionisation energy’ as the difficulty in removing electrons from an atom to create a positively charged ion. When people talk about the first ionisation energy it is the amount of energy required to remove an electron from each atom in a mole of gaseous atoms (definition of a mole coming up later!) and is normally quoted in kilojoules per mole.
  12. You should be able to look at a graph of first ionisation energies changing across a period and explain why the increases and decreases give evidence for the filling of levels and sub-levels.
  13. The second, third or higher ionisations are simply removing another electron from an already ionised atom; if you think about it each successive ionisation energy should be higher than the last as the electrons are more attracted to the positively charged ion.

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Example Questions for Atomic Structure

  1. Explain how a mass spectrometer separates atoms based on their mass to charge ratio (M/Z).
  2. Give the electronic configuration of Ne in terms of s,p and d orbitals.
  3. Explain the difference between the three fundamental particles that make up at atom in terms of both mass and charge.

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Remember it!

    • Remember the masses and charges of protons, electrons and neutrons.
    • Learn how a mass spectrometer works and practise reading the spectra.
    • Make sure you can draw the s, p and d orbitals.
    • Get a clear understanding of ‘ionisation energy’ and make sure you can explain the increases and decreases across a period. Hint: it’s due to the filling of electron levels… atoms are more stable when they have full electronic orbitals.
    • Practise filling out the s, p and d orbitals for different elements. You’ll be required to do this in the exam and it’s an easy way to pickup marks once you know how to fill the levels.
    • Always fill the orbital with the lowest energy- learn the order 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p.