SME
Grade 10 Science · Problem type
Oxidation numbers: the atom to find
Use this for “What is the oxidation number of S in H₂SO₄?” or in SO₄²⁻.
Diagram
The oxidation numbers of all the atoms add up to the charge of the particle.
This is an example. Type your own values to start a new problem.
x
+
h
×
(+1)
+
o
×
(−2)
=
q
Formulas
x
+
h
×
(+1)
+
o
×
(−2)
=
q
6 + 2 × (+1) + 4 × (−2) = 0
Assumptions
•
Hydrogen is +1 and oxygen −2 in most compounds.
•
The oxidation numbers of all the atoms add up to the charge: 0 for a neutral compound.
Step-by-step
WE KNOW
h = 2, o = 4, q = 0
FIND
oxidation number of the sulfur (x)
Step 1 · Find oxidation number of the sulfur (x)
Use x + h × (+1) + o × (−2) = q
Take 1 from the charge for each hydrogen and add 2 for each oxygen.
x
=
q
−
h
+
2
×
o
x
=
0
−
2
+
2
×
4
x
=
0
−
2
+
8
x
=
6
Check
Put the numbers back in. Both sides should match.
6 + 2 × (+1) + 4 × (−2) = 0 ✓
Topic check
See what you know: 5 questions on this topic
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Oxidation-reduction reactions, electrochemistry, electrolysis and corrosion
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