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Unformatted text preview: t in (1) O2
and O3 molecules; (2) the peroxides, which contain the
O2 2− group; and the (3) the rare superoxides, which con−
tain the O2 group.
(d) In ternary acids (oxoacids), hydrogen usually bonds to an
O atom, not to the central atom. (Exceptions are phosphorous acid, H3 PO3 , where one H is bonded to P, and
GChem I 9.7 hypophosphorous acid, H3 PO2 , where two H are bonded
(e) The least electronegative atom is usually the central
(f) For ions or molecules that have more than one central
atom, the most symmetrical skeletons possible are used.
2. All the valence electrons must be accounted for.
3. Usually, each atom in a Lewis structure acquires an electron
conﬁguration with an outer-shell octet. (The outer shell of H
has only 2 electrons.) Nonmetals of the third period and beyond may be surrounded by more than eight electrons (expanded valence). (The outer shell of Be has only four electrons, that of B only six electrons.)
4. Usually, all the electrons in a Lewis structure are paired.
5. Often, both atoms in a bond...
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