Redox Reactions and Oxidation Numbers

Vocabulary flashcards covering the definitions, rules, and naming conventions of redox reactions, oxidation numbers, and disproportionation based on the Chapter 7 lecture notes.

Redox Reaction

An oxidation-reduction reaction characterized by electron transfer and changes in oxidation number.

Oxidation

The loss of electrons ($oil$), gain of oxygen, or loss of hydrogen during a chemical reaction.

Reduction

The gain of electrons ($reg$), loss of oxygen, or gain of hydrogen during a chemical reaction.

Oxidation Number (Oxidation State)

A number given to each atom or ion in a compound that shows its degree of oxidation; it can be positive, negative, or $0$.

Elemental Form Rule

The rule stating that the oxidation number of an atom in its pure, elemental form is $0$, such as in $N_2(g)$, $O_2(g)$, $H_2(g)$, $Cu(s)$, $S(s)$, $C(s)$, $Cl_2(g)$, $Br_2(l)$, or $I_2(s)$.

Molecule Neutrality Rule

In a neutral molecule, the sum of the oxidation numbers of all atoms must be $0$, such as in $H_2O$, $Fe_2O_3$, $H_2SO_4$, and $CaCO_3$.

Group 1 Rule

The rule stating that Group 1 elements always have an oxidation number of $+1$.

Group 2 Rule

The rule stating that Group 2 elements always have an oxidation number of $+2$.

Fluorine Rule

The rule stating that Fluorine is always $-1$.

Hydrogen Rule

Hydrogen is $+1$, except in metal hydrides such as $NaH$, where it is $-1$.

Oxygen Rule

Oxygen is normally $-2$, except in peroxides where it is $-1$, and in $F_2O$ where it is $+2$.

Ion Sum Rule

The sum of the oxidation numbers in an ion is equal to the charge on the ion, such as in $SO_4^{2-}$, $CO_3^{2-}$, or $NO_3^-$.

Electronegativity Naming Rule

The rule stating that the more electronegative element is assigned the more negative oxidation number.

Roman Numerals in Naming

Used in brackets to indicate oxidation numbers to distinguish between atoms in different compounds, such as iron(II) chloride ($FeCl_2$) and iron(III) chloride ($FeCl_3$).

"-ate" Ending

The suffix used for names of ions containing oxygen and one other element, such as $NaNO_3$ being sodium nitrate(V).

"-ic" Ending

The suffix used for the names of inorganic acids containing oxygen, such as $H_3PO_3$ being called phosphoric(III) acid.

Oxidation Half-Equation

A representation of a substance losing electrons, modeled as $X \rightarrow X^{n+} + ne^-$.

Reduction Half-Equation

A representation of a substance gaining electrons, modeled as $Y^{n+} + ne^- \rightarrow Y$.

Oxidising Agent (Oxidant)

The reactant that gains electrons and is reduced while causing another substance to be oxidised.

Reducing Agent (Reductant)

The reactant that loses electrons and is oxidised while causing another substance to be reduced.

Disproportionation

A 'self-reduction-oxidation' reaction where atoms of the same element are both reduced and oxidised in the same reaction, such as adding chlorine to cold aqueous sodium hydroxide.