Oxidation Numbers

[Meigan Wu 2E]

How do you know the oxidation number for an atom of an element?

[Mariam Baghdasaryan 4F]

Step 1. Atoms in their elemental state have an oxidation number of 0.
Step 2. Atoms in monatomic (i.e. single atom) ions have an oxidation number equal to their charge.
Step 3. In compounds: fluorine is assigned a −1 oxidation number; oxygen is usually assigned a −2 oxidation number (except in peroxide compounds where it is −1, and in binary compounds with fluorine where it is positive); and hydrogen is usually assigned a +1 oxidation number except when it exists as the hydride ion, H−, in which case rule 2wins.
Step 4. In compounds, all other atoms are assigned an oxidation number so that the sum of the oxidation numbers on all the atoms in the species equals the charge on the species.

https://www.khanacademy.org/science/che ... ion-number

[Parth Mungra]

For many atoms, you can observe their position in the periodic table and their valence electrons. Fluorine, for example, has 7 valence electrons, 2 in the 2s subshell, and 5 in the 2p subshell (2 in the 2px, 2 in the 2py, and 1 in the 2pz orbitals). Because of this, it needs to gain an extra one electrons to have 8 total valence electrons, thus making it's oxidation state 1-. This does not work all the time, I am sure because there are always some exceptions. Some periodic tables state some of the common oxidation states of elements as well.

[annabel 2A]

When and why does hydrogen exist as hydride?