Given the balanced equation representing a reaction:
o2 --> o + o
what occurs during this reaction?
(1) energy is absorbed as bonds are broken.
(2) energy is absorbed as bonds are formed.
(3) energy is released as bonds are broken.
(4) energy is released as bonds arc formed.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.