Atomic structure
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When a question is asked what group is a metal in if it has a big jump from the third to the fourth ionisation energy, I know it is in the third shell. But why?
Rev replies…
From your question you clearly understand about electronic structure. It is best if we look at some data for magnesium.
First IE 736 kJ mol-1
Second IE 1448 kJ mol-1
Third IE 7740 kJ mol-1
Fourth IE 10470 kJ mol-1
Electrons in the same outer shell have similar ionisation energy shown by the first and second IE above. A big jump in the ionisation energy to remove the third electron ( about four times) means the electron is being removed from and inner shell. All theses energies are due to the attraction of the nucleus for the electron. Electron in the outer most shell are being shielded by the full inner shells ( this means they cannot experience so much attraction by the nucleus and are further away from the nucleus). Once the outer shell electrons have been removed it is necessary to break into a full shell to remove the next one. This is difficult and needs much more energy hence the big jump.
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updated: 21 August 2003
