Assign oxidation numbers to each atom in Borax, Na2B4O7, a mineral used in laundry detergent. (LO 4.18)

Oxidation numbers are assigned to atoms in a compound to indicate the degree of oxidation or reduction of each atom. They help in understanding electron transfer in redox reactions. The rules for assigning oxidation numbers include that the oxidation number of an element in its elemental form is zero, and for monoatomic ions, it equals the charge of the ion.

Borax contains the polyatomic ion B4O7^2-, which consists of boron and oxygen atoms. Understanding the structure and charge of polyatomic ions is crucial for assigning oxidation numbers correctly. Each atom within the polyatomic ion contributes to the overall charge, which must be balanced with the oxidation numbers assigned to the other elements in the compound.

When assigning oxidation numbers, it is essential to ensure that the sum of the oxidation numbers equals the overall charge of the compound. In the case of Borax, Na2B4O7, the sodium ions (Na+) contribute a +2 charge, which must be balanced by the oxidation numbers of the boron and oxygen atoms in the B4O7^2- ion. This balancing act is key to accurately determining the oxidation states.