Uploaded August 2025 | Updated September 2026, 2 weeks ago
Oxidation Numbers
Dr. DeBacco
Oxidation Numbers
Oxidation numbers (or oxidation states) show how many electrons they have gained or lost relative to their elemental state.
This keeps track of electron ownership in reactions, especially redox (reduction-oxidation) reactions.
What Do They Represent?
They indicate the charge an atom would have if electrons were transferred completely.
Positive number → atom lost electrons (oxidized).
Negative number → atom gained electrons (reduced).
Basic Rules to Assign Oxidation Numbers
Free elements (uncombined): 0
Example: O₂, Na, Cl₂ → all have oxidation number 0
Monatomic ions: Equal to their charge
Example: Na⁺ = +1, Cl⁻ = –1
Oxygen: Usually –2 (except in peroxides like H₂O₂, where it’s –1)
Hydrogen: +1 when bonded to nonmetals, –1 when bonded to metals
Fluorine: Always –1 in compounds
The sum of oxidation numbers in a neutral compound = 0 In polyatomic ions, it equals the ion’s charge
Oxidation States in the Periodic Table
Hydrogen = +1 (×2) → +2
Oxygen = –2
Total = 0
Why They are Useful
To determine if redox reactions occurred.
To balance redox equations properly.
To understand electron movement between atom
Link to Lecture Slides: drive.google.com/file/d/1jhrWu8so7LAoZ1j3vwjHtZBB9Pqu62wi/view?usp=drive_link
*Due to the description character limit the full work cited for "Oxidation Numbers" can be viewed at... docs.google.com/document/d/1JH1OIo_jSe0tOmVxnhcXeaG-IwL_wPhe/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
Oxidation Numbers
Dr. DeBacco
Oxidation Numbers
Oxidation numbers (or oxidation states) show how many electrons they have gained or lost relative to their elemental state.
This keeps track of electron ownership in reactions, especially redox (reduction-oxidation) reactions.
What Do They Represent?
They indicate the charge an atom would have if electrons were transferred completely.
Positive number → atom lost electrons (oxidized).
Negative number → atom gained electrons (reduced).
Basic Rules to Assign Oxidation Numbers
Free elements (uncombined): 0
Example: O₂, Na, Cl₂ → all have oxidation number 0
Monatomic ions: Equal to their charge
Example: Na⁺ = +1, Cl⁻ = –1
Oxygen: Usually –2 (except in peroxides like H₂O₂, where it’s –1)
Hydrogen: +1 when bonded to nonmetals, –1 when bonded to metals
Fluorine: Always –1 in compounds
The sum of oxidation numbers in a neutral compound = 0 In polyatomic ions, it equals the ion’s charge
Oxidation States in the Periodic Table
Hydrogen = +1 (×2) → +2
Oxygen = –2
Total = 0
Why They are Useful
To determine if redox reactions occurred.
To balance redox equations properly.
To understand electron movement between atom
Link to Lecture Slides: drive.google.com/file/d/1jhrWu8so7LAoZ1j3vwjHtZBB9Pqu62wi/view?usp=drive_link
*Due to the description character limit the full work cited for "Oxidation Numbers" can be viewed at... docs.google.com/document/d/1JH1OIo_jSe0tOmVxnhcXeaG-IwL_wPhe/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
