Oxidation state refers to any possible charge an ion of an element can have. For ex. Sodium (Na) has a
+1 oxidation state. You can find a list of possible oxidation states in the upper right corner of any
element’s box on the PT. Some elements have multiple oxidation states = more than one (+) or (-) value
for the number of electrons lost or gained, respectively.
Valence electrons: only those electrons found in the OUTERMOST PEL of an atom. THESE are
the electrons that enter into chemical reactions. The number of valence electrons is equal to
the Roman numeral at the top pf an “A” group column. For example. The Halogens, like
Bromine, all have VII or 7 valence electrons in their outermost PEL.
Another way to determine valence electrons is to write the ABREVIATED electron configuration
(EC) For an atom of any element, then look to the section of the EC with the highest PEL
number…these are your valence electrons. For example, Bromine (Br), has an abbreviated
configuration of [Ar] 4s23d104p5. The highest PEL following the [Ar] is PEL 4. With 2 electrons in
the 4s and 5 in the 4p, Bromine has 2 + 5 = 7 valence electrons.
Read your additional notes on PT-10 in your packet.