CHEM 205 Lecture Notes - Lecture 7: Alkali Metal, Roman Numerals, Oxidizing Agent
12 Mar 2018
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Week 7: loss of e-= oxidation, gain of e-= reduction. Oxidation state (=oxidation #: denoted using roman numerals (cid:523)so we don(cid:495)t confuse it with real charges(cid:524, describes if atom is e rich (hogging e-(cid:494)s in a bond(cid:524) vs. e poor (other atom is hogging e-(cid:494)s(cid:524) Equal sharing between atoms no missing (+n) extra (-n) As if ionic (but no full charges really present) Trends (easier to see when draw structures in chapter 8): h in all molecules: +i, o in most compounds: -ii, f in all compounds: -i, o in peroxides (o2. Classic redox reactions: combustion & corrosion: combustion = burning substances in presence of oxygen (especially organic compounds ex: natural gas, o becomes reduced (formally gains 2 e- per o atom, o(cid:495)s oxidization number goes down. If molecular: use trends, leave variable ox. #-atoms for last. If ionic: divide into ions 1st, then assign ox. #(cid:495)s as above. )n all cases: sum of ox. #(cid:495)s= net charge on species: contains (cid:498)high(cid:499) ox.
