3: Oxidation Numbers Flashcards
What is oxidation?
Loses electrons or increase in oxidation number
What is reduction?
Gains electrons or decrease in oxidation number
What is the oxidation number of uncombined elements and explain?
0
Haven’t accepted or donated any electrons
What is the oxidation number of a monotomic ion?
Same as it’s charge
What is the oxidation number of a molecular ion?
Sum of the oxidation numbers of each atom equals the overall charge
What is the oxidation number of a neutral compound?
Sum of the oxidation numbers is 0
What is the oxidation number of hydrogen?
+1
Except in metal hydrides when its -1, and 0 in H2
What is the oxidation number of oxygen?
-2
Except in peroxides when its -1, and 0 in O2
Where will the electrons be in the ionic half equation for reduction?
Reactant + Electrons -> Product
Where will the electrons be in the ionic half equation for oxidation?
Reactant -> Product + Electrons
What is the oxidation number of fluorine?
-1
In general what are the oxidation numbers of metals?
Positive
In general what are the oxidation numbers of non-metals?
Negative
What do roman numerals show in a compound?
Oxidation number of that ion
What does the suffix -ate suggest?
The compound contains oxygen
What charge should you assume is on a compound if one is not given?
0
What charge is a cation and anion?
Cation - positively charged
Anion - Negatively charged
What does redox mean?
Reduction and oxidation is occurring simultaneously
What is an oxidising agent?
Something that gets reduced and causes something to get oxidised
What is a reducing agent?
Something that gets oxidised and causes something to get reduced
What occurs to the oxidation number when one electron is lost?
Increases by 1
What occurs to the oxidation number when one electron is gained?
Decreases by 1
What do metals normally undergo in a redox reaction?
Donate electrons to form positive ions (positive oxidation numbers)
What do non-metals normally undergo in a redox reaction?
Gain electrons to form negative ions (negative oxidation numbers)
What is a disproportionation reaction?
Redox reaction where an element from a single species is simultaneously oxidised and reduced
When combining half equations what must you ensure with the number of electrons?
Same number must be on each side so they can cancel out
What can you add to balance redox reactions?
Electrons
H+ ions
Water
