Atomic structure
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Hi, I just wanted to find out what are the factors that affect the first ionisation energy...in detail. Just can't seem to undersand it clearly.
220908
Corrie writes ...
Ionisation energy is a measure of the attraction between the electron being lost and the positive nucleus.
It is therefore affected by the nuclear charge: the greater the nuclear charge (across a Period, for instance) the greater the attraction.
It is also affected by the distance of the electron being lost from the nucleus. Broadly speaking, electrons in the same shell (i.e. in atoms across a Period) are a similar distance from the nucleus, so the increasing nuclear charge is the most important factor affecting ionisation energy. However, electrons in new outer shells (i.e. down a Group) are much further from the nucleus and thus experience a much weaker attraction despite the increase in charge of the nucleus.
A further factor is the amount of shielding (screening) of the nuclear charge by the completed shells of electrons between the nucleus and the outer electron being lost. Across a Period this changes little, but down a Group, as new shells are added, this shielding effect increases.
There are other, more subtle factors that affect ionisation energy but I won't go into these now.
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updated: 23 September 2008
