Here are the oxidation numbers for each element in the formulas listed on your worksheet. I have calculated them using the rules provided at the bottom of the page (like Oxygen usually being -2, Hydrogen +1, and the total sum matching the charge).
Final Answer:
1.
Cl₂: Cl =
0
2.
Cl⁻: Cl =
-1
3.
Na: Na =
0
4.
Na⁺: Na =
+1
5.
O₂: O =
0
6.
N₂: N =
0
7.
Al³⁺: Al =
+3
8.
H₂O: H =
+1, O =
-2
9.
NO⁻: N =
+5, O =
-2
10.
NO₂: N =
+4, O =
-2
11.
Cr₂O₇²⁻: Cr =
+6, O =
-2
12.
KCl: K =
+1, Cl =
-1
13.
NH: N =
-3, H =
+1
14.
CaH₂: Ca =
+2, H =
-1 *(Note: H is -1 because it is bonded to a metal)*
15.
SO²⁻: S =
+6, O =
-2
16.
Na₂O₂: Na =
+1, O =
-1 *(Note: This is a peroxide)*
17.
SiO₂: Si =
+4, O =
-2
18.
CaCl₂: Ca =
+2, Cl =
-1
19.
PO₄³⁻: P =
+5, O =
-2
20.
MnO₂: Mn =
+4, O =
-2
21.
FeO: Fe =
+2, O =
-2
22.
Fe₂O₃: Fe =
+3, O =
-2
23.
H₂O₂: H =
+1, O =
-1 *(Note: This is a peroxide)*
24.
CaO: Ca =
+2, O =
-2
25.
H₂S: H =
+1, S =
-2
26.
H₂SO₄: H =
+1, S =
+6, O =
-2
27.
NH₄Cl: N =
-3, H =
+1, Cl =
-1
28.
K₃PO₄: K =
+1, P =
+5, O =
-2
29.
HNO₃: H =
+1, N =
+5, O =
-2
30.
KNO₂: K =
+1, N =
+3, O =
-2
Parent Tip: Review the logic above to help your child master the concept of oxidation number worksheet.
