What is the oxidation number of H2O?

    0

    Overall 0. The H atoms have a ON of +1 each (or plus two altogether) and O is -2.
    This comes straight from the oxidation number (or ON cuz I’m lazy) rules. The particular rules that I drew from are bolded;
    The sum of all by itself equals 0 on a neutrally charged molecule.
    ##H_2O## has no positive or negative charge thus its overall ON must be zero 0.
    Hydrogen has an ON of +1 when with non-metals.
    In the water molecule H is with O. As oxygen is not a metal each hydrogen molecule must have an ON of -1. As there are two H atoms the total ON for H is ##-1*2=-2##.
    Oxygen has an ON of -2
    As the rule states in this case O has an ON of -2.
    The O and H ONs can be added together to get an overall ON. ##-1(2) + -2 = 0##. As can be seen this works out with the first rule!
    I found this a good overall ON explanation.Tyler DeWitt – How To Calculate Oxidation Numbers

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