REduction
- Previously : What happened to oxygen when it reacted to make a predict.
- Now : When any element gains an electron
Oxidation
- Back then: what happened to any element that reacted with oxygen.
- Now: When elements looses electrons.
REdox
![Picture](/uploads/2/9/9/7/29971125/9282431.png)
- Reduction and oxidation NEVER happen alone they always happen together.
- LEO…the lion says…GER
- L . lose E . electrons O. oxidized
- G . gain E . electrons R. reduced
- ANY reaction where the oxidation umber of an element is different on the two sides of the chemical equation is a redox equation.
- Mg + 2HCl ---> MgCl2 + H2
- Redox reactions are represented with half reactions.
Agents
- Reducing agent: an element that serves as the sourcs of electorn. ( goes with the oxidized number )
- Oxidizing Agent: an element that receives the electrons is known as the oxidizing agen. ( goes with reduced number)
Oxidation Numbers
- Oxidation numbers can be assigned using the periodic table, if the compound is an ionic compound.
- Covalent compounds are made of 2 non-metals, which are expected to be negative. Because covalent compounds are neutral it's not possible for them to have all negative . Only the more electronegative element stays negative and the least elecrto negative changes to positive.
- The oxidation number is different from it's formal charge. Oxidation numbers is another way help us keep track of electrons in a chemical reaction.
Rules for
Determining Oxidation Numbers
- The oxidation number for any UNcombined element is ZERO
- The charge of an ion with a plus or minus as a superscript is equal to the elements charge
- Oxygent's oxidation number is always -2 EXCEPT in peroxides ( H2O2) where oxygen is equal to -1, ALSO when oxygen bonds with fluorine the number will be +2
- Hydrogen's oxidation number is always +1 EXCEPT when it bonds with metals to form metal hydrides where hydrogen will be -1 ALSO in the polyatomic ion NH4 where it is also -1.
- The SUM of the oxidation numbers for a compound must equal zero.
- The sum of the oxidation number is the formula of polyatomic ion is equal to it's charge.
Information was presented in class.