Oxidation Numbers Flashcards
What does an oxidation number show?
Shows how many electrons an atom has donated or accepted to from an ion or part of a compound.
O.N of Uncombined Elements?
0 (haven’t accepted or lost electrons)
O.N of Elements bonded to identical atoms?
0 e.g H₂
O.N of simple monatomic (one atom) ions?
Same as its charge. e.g Mg²⁺ = +2
O.N of a molecular ion?
Same as the overall charge.
This can be found by adding up the individual oxidation numbers of the atoms in the compound.
O.N of a neutral compound?
0
O.N of combined oxygen?
-2 (eg H₂O)
O.N of combined oxygen in peroxides?
-1 (eg H₂O₂)
ON of Combined Hydrogen?
+1 eg NH₃
ON of combined Hydrogen in metal hydrides?
-1 (eg LiH)
What are Roman Numerals used for?
To show the Oxidation Number if an element has multiple O.N’s or isn’t in it’s ‘normal’ state. eg III = 3
Where are roman numerals written in an equation?
After the element they correspond to.
What do Ions with names ending in ‘-ate’ contain?
Oxygen and another element.
eg Nitrates contain Nitrogen and Oxygen
Give some examples of ‘-ate’ ions.
Sulphate, Nitrate, Chlorate, Carbonate.
If roman numerals are placed after a -ate compound, what does this correspond to and why?
The O.N of the Non Oxygen atom, eg nitrogen in Nitrate.
It is there as the other element may form different -ate ions.
