Structure 3.1.6 - the oxidation state is a number assigned to an atom to show the number of electrons transferred in forming a bond. it is the charge that the atom would have if the compound were composed of ions.
the terms oxidation number and oxidation state are used interchangeably
see 3.1.9 variable oxidation states (HL)
oxidation can involve elements other than oxygen
when magnesium reacts with oxygen, it is oxidised and forms the ionic compound
from the perspective of magnesium
as magnesium loses electrons when reacting with non-metals, the term oxidation can be extended to other reactions not involving oxygen
(oxidation is applied to any electron transfer reaction - an increase in oxidation state)
oxidation is
- addition of oxygen
- removal of hydrogen
- electron loss
- increase in oxidation state
an OILRIG cat
anode happens at (oxidation is lose electrons, reduction is gain electrons) at cathode
oxidation states are a measure of how electrons are distributed
in ionic substances, the oxidation state is the same as the ionic charges
in covalent substances, the electron distribution depends on the polarity of the bond and the relative electronegativities of the bonding atoms.
- if an atom is bonded to a more electronegative atom, it loses some control over its electrons and has a positive oxidation state
- if an atom is bonded to a less electronegative atom, it gains control over more electrons and has a negative oxidation state
rules
- free elements have oxidation state of 0
- in simple ions, the oxidation state is the same as the ionic charge
- the oxidation state of all atoms of a neutral compound sum to 0
- oxidation states of all atoms in a polyatomic ion sum to the charge of the ion
- the oxidation state for an element in a compound is the same as the charge on its most common ion
- F has the oxidation state of -1 in all compounds (since it’s the most electronegative)
- O has the oxidation state of -2 except:
- O has the oxidation state of -1 in peroxides and when bonded to fluorine
- Cl has a positive oxidation state when bonded to F or O
- H has the oxidation state of +1, except when bonded to Group 1 and Group 2 (forming ionic hydrides)
- the oxidation state of a transition metal in a complex ion can be worked out from the charge on the ligands
IUPAC nomenclature
correspondingly,