Chemisty Oxi Rules

Oxidation number (O.N.) for an atom in its elemental form

$$0$$

Examples of atoms in their elemental form that have an O.N. of $0$

$\text{Na}$, $\text{O}_2$, $\text{Cl}_2$

Oxidation number for a monoatomic ion

Equal to the ion's charge

Sum of O.N. values for all atoms in a neutral compound

$$0$$

Sum of O.N. values for all atoms in a polyatomic ion

Equal to the ion's charge

Oxidation number for Group 1A(1) elements in compounds

$$+1$$

Are there exceptions to the $+1$ oxidation number for Group 1A(1) elements in compounds?

No, it is $+1$ in all compounds.

Oxidation number for Group 2A(2) elements in compounds

$$+2$$

Are there exceptions to the $+2$ oxidation number for Group 2A(2) elements in compounds?

No, it is $+2$ in all compounds.

Oxidation number for hydrogen when combined with nonmetals

$$+1$$

Oxidation number for fluorine when combined with metals

$$-1$$

Oxidation number for fluorine when combined with boron

$$-1$$

Oxidation number for oxygen in peroxides

$$-1$$

Oxidation number for oxygen in standard compounds (excluding peroxides and fluorine)

$$-2$$

Element with which oxygen does NOT have an O.N. of $-2$

Fluorine ($\text{F}$)

General oxidation number for Group 7A(17) halogens

$$-1$$

Oxidation number of Group 7A(17) halogens when combined with metals

$$-1$$

Usual oxidation number of Group 7A(17) halogens when combined with nonmetals

$$-1$$

Nonmetal exception that prevents Group 7A(17) halogens from having an O.N. of $-1$

Oxygen ($\text{O}$)

Oxidation number of a Group 7A(17) halogen when combined with another halogen lower in the group

$$-1$$