Atomic structure
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As ionization energy of zinc is more than that of gallium but the atomic radius of gallium is smaller than that that of zinc. Please help me to sort out this problem.
280708
Ulex writes
Ionisation energy and atomic radius are both influenced by:
• the orbital of the electron being removed
• the charge on the nucleus
• the extent of the screening of the nucleus by inner electrons
The electronic configurations of the two elements are:
Zn: [Ar]3d104s2, nuclear charge 30+, 1st IE = 906 kJ mol-1, rm = 0.137 nm
Ga [Ar]3d104s24p1, nuclear charge 31+, 1st IE = 579 kJ mol-1, rm = 0.153 nm
The screening of the outermost electron from the nucleus is greater in gallium than in zinc (more inner electrons), and the electron being removed is 4p in gallium but 4s in zinc. These factors outweigh the nuclear charge, being greater in gallium than in zinc. So gallium’s ionisation energy is the lesser of the two, and its atomic radius greater (not less, as you suggest).
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updated: 28 July 2008
