Post on 15-Jan-2016
Notes – Determining Oxidation Number
Who Gains? Who Loses?
Background Information/Terms• Ion- an atom with a positive or
negative electric charge.
• Valence energy level- the outermost (highest) energy level.
• Valence electrons- the electrons found in the outermost energy level.
Background Information/Terms• Family numbers- the numbers at the top of the
periodic table that (with some modification) tell how many valence electrons an atom has.
• Octet rule- a rule (that is generally true) which states that an atom with a full valence energy level is stable.
• Oxidation number - the number of electrons that an atom gains, loses or shares in order to form chemical bonds.
Facts about Elements and Their Oxidation Number - Metals
• Metals lose their valence electrons when they become ions. This gives metals a full outermost energy level.
• Metal ions have a positive (+) charge.
• The number of electrons a metal loses becomes its oxidation number.
Facts about Elements and Their Oxidation Number - Nonmetals
• Nonmetals gain electrons until they get 8 electrons in their outermost energy level.
• Nonmetal ions have a negative (-) charge.
• The number of electrons a nonmetal gains becomes its oxidation number.
Oxidation number
• Oxidation number - the number of electrons that an atom gains, loses or shares in order to form chemical bonds.
• The oxidation number determines two things:– How the element will bond
– What elements will bond with it
Review• Elements want to have a stable atomic structure.
• Stable atoms have full outer energy levelsIf an element has only one energy level, it is full with 2 electrons
• Although the third levels hold more than 8, atoms think their energy levels are full with 8 electrons
• Some elements gain electrons to get full while other will lose electrons to empty out a level.
Summary
It is easier to gain one or two electrons than to lose 6 or 7 and vice versa.
Family # # of valence electrons
gain or lose Oxidation number
1 1 Lose 1 + 1
2 2 Lose 2 + 2
13 3 Lose 3 + 3
14 4 Gain or lose 4 +/- 4
15 5 Gain 3 - 3
16 6 Gain 2 -2
17 7 Gain 1 -1
18 8 Already full 0