Shells and Orbitals Explained

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Shells and Orbitals Explained

By T.Cox 

Energy Levels or Shells ~ 

     Ok, just before I start parts of this are taken from the text book, so that I give you exactly what happens and there is no room for mis-interpretation or me just explaining it wrong! Although this ensures what I'm saying is correct It does contain some scinency words which no one likes or understands so Ill do my best to explain what's going on as we delve into the murk depths that is quantum physics. 

Oh and as a final note before we begin I found a little quote from a top scinency boffin to make those among us who don't feel 100% confident with it - "I think its safe to say that no one understands quantum mechanics"  - Richard P. Feynman, someone who knows about physics. Puts things in perspective nicely I think... 

Anyways, onwards. 

     As we know, or at least you would if you have read my notes on ionisation energies, that successive ionisation energies provide evidence for, the presence of shells and the number of electrons within an atom. Quantum Numbers (the term isn't important - you don't need to know what it means, just remember that its there) are used to describe the electrons in an atom. The principal (first) quantum number, n, indicates the shell which a particular electron occupies. Different shells have different quantum numbers. The larger the value of n, the further away from the nucleus the electron is and the higher the energy level. A shell is the same thing as the energy level of the principal quantum number. The first four shells of electrons for each element hold 2n squared electrons each. (shell 1 has 2 electrons, shell 2 has 8, shell 3 has 18, shell 4 has 32, etc...)

Atomic Orbitals ~

      These are the areas in which we think the electrons are (yup, your right - we don't actually know where they are we are just guessing!). There are rules about where the electrons could be within each shell. We think that electrons occupy orbitals which are basicly an area where they could be. Something like a cloud. Each shell is made up of atomic orbitals, each atomic orbital can hold a maximum of 2 electrons. There are 4 different type of orbital - s,p,d and f, each with their own particular shape. 

S-orbitals, The s-orbital has a spherical (o) shape, from n=1 (n being the principal quantum number) upwards contains one s-orbital. This gives a total of 1 x…


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