University:
Georgia Southern University
Course:
CHEM 1310 | Comprehensive General Chemistry
Academic year:

2024
Views:

481

Pages:

1
Author:

Jalen W.

Oxidation Numbers Definition: An oxidation number is a numerical value assigned to an element in a molecule or ion to reflect qualitatively the charge on the atom. In a molecule or polyatomic ion the oxidation number of an element is “pseudo-charge.” Guidelines for Assigning Oxidation Numbers 1. Under STP conditions the oxidation number for elements is ZERO. Remember except for the noble gases (which are monatomic) elements that are in the gaseous under STP conditions are diatomic. Their oxidation is still assigned a value of ZERO 2. Bromine and mercury are liquid at STP; bromine exists, as Br 2 and mercury is Hg. Both have assigned oxidation numbers of ZERO. 3. Group 1A and 2A elements ALWAYS have an oxidation state value of +1 and +2 respectively. 4. The following elements only have one assigned oxidation state value: Aluminum is +3 Cadmium is +2 Zinc is +2 Silver is +1 Fluorine is -1 5. Oxidation rules for hydrogen and oxygen ions a) Hydrogen as an ion is assigned a value of +1 unless it is bond to an alkali (group 1A) or to an alkaline earth (Group 2A) cation, then it is given a value of –1. H-1 is referred to as the hydride ion and H+ is known as the hydronium ion. b) Oxygen as an ion is assigned a value of –2. O-2 is referred to as the oxide ion. Oxygen ion can also have a value of –1 (O-1) and is referred to as the peroxide ion. It can also be assigned a charge of –1/2 (O-1/2) and is known as the superoxide ion – which is very unstable. Peroxides and superoxide ions are most often seen when these ions bind with the hydronium ion and/or Group 1A and 2A metals. 6. The summation of oxidation number is a compound MUST add up to ZERO 7. The summation of the oxidation number in a polyatomic ion will ALWAYS be equal to the charge of that polyatomic ion.