CHEM 106 Lecture Notes - Lecture 24: Effective Nuclear Charge, Alkaline Earth Metal, Electron Configuration
13 Mar 2019
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Section 22. 2 - periodic and chemical properties of. 11:39 pm: the main group or representative elements, as defined in chapter 2, appear in groups 1, 2, and 13 18 of the periodic table of the elements. These eight groups contain 44 naturally occurring elements, including five for which no stable iso- topes are known: fr, ra, po, at, and rn. Relatively little is known about the chemistry of francium or astatine, both of which are exceedingly rare. Their first ionization energies and electronegativities decrease with increasing atomic number down a group and increase across a row. In general, electron affinities become more negative across a row. We have explored how all of these periodic trends are related to changes in the effective nuclear charge experienced by valence electrons as atomic numbers increase and inner shells fill with electrons. A survey of the main group elements reveals a range of physical and chemical properties.
