Waiting for answer This question has not been answered yet. You can hire a professional tutor to get the answer.
How do you calculate the oxidation number of an element in a compound?
You assign to the elements in a compound by using the Rules for Oxidation Numbers.
-
The oxidation number of a free element is always 0.
-
The oxidation number of a monatomic ion equals the charge of the ion.
-
The oxidation number of ##"H"## is +1, but it is -1 in when combined with less electronegative elements.
-
The oxidation number of ##"O"## in is usually -2, but it is -1 in peroxides.
-
The oxidation number of a Group 1 element in a compound is +1.
-
The oxidation number of a Group 2 element in a compound is +2.
-
The oxidation number of a Group 17 element in a binary compound is -1.
-
The sum of the oxidation numbers of all of the atoms in a neutral compound is 0.
-
The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.
EXAMPLE:
What is the oxidation number of ##"Cr"## in ##"CrCl"_3## ?
Solution:
We use what rules we can to determine the oxidation numbers.
Rule 7 states that the oxidation number of Cl is -1.
We write the oxidation number of the element above its symbol and the total for 3 Cl atoms below the symbol.
This gives ##"Cr"stackrelcolor(blue)("-1")("Cl")_3## ##color(white)(mmmmmmll)stackrelcolor(blue)("-3"color(white)(mm))##.
Rule 8 states the numbers along the bottom must add up to zero. So the number under ##"Cr"## must be +3.
This gives ##"Cr"stackrelcolor(blue)("-1")("Cl")_3## ##color(white)(mmmmm)stackrelcolor(blue)("+3"color(white)(ll)"-3"color(white)(mm))##.
There is only one ##"Cr"## atom, so its oxidation number is +3.
This gives ##stackrelcolor(blue)(+3)("Cr")stackrelcolor(blue)("-1")("Cl")_3## ##color(white)(mmmmm)stackrelcolor(blue)("+3"color(white)(ll)"-3"color(white)(mm))##.
The oxidation number of ##"Cr"## in ##"CrCl"_3## is +3.
Here is a chart showing the oxidation numbers of the atoms in some common elements and compounds.
