Redox Chemistry

Oxidation-reduction reactions ("redox" for short) involve the transfer of electrons. There are two parts to a redox reaction. OXIDATION: when an element LOSES an electron, and REDUCTION: when an element GAINS an electron.
A shortcut to remember this is: OIL RIG. (Oxidation Is Loss, Reduction Is Gain). Substances that are reduced are called oxidizing agents and substances that are oxidized are called reducing agents.
When substances are not ionic and it is harder to "see" where the electrons are going, you have to rely on electronegativity. In covalently bonded molecules, you have to look at the more electronegative of the elements (particularly groups 16 & 17). These elements have high electronegativities (ENs) because they don't want to lose the valence electrons they already have. The opposite holds true for groups 1 & 2; low ENs because they don't have a need to keep the valence electrons they already have.
Electronegativity Table (Source: www.mikeblaber.org)
The more electronegative atom is treated as if it is being reduced by gaining electrons from the other atom. The less electronegative atom is treated as if it is being oxidized by losing electrons to the other atom.
When oxidation occurs, the charge on the ion increases. The more electrons lost, the more positive the ion becomes. Manganese has two oxidation states (two types of ions). Manganese (II) has a charge of Mn+2 because two electrons were removed from the manganese atom, and manganese (IV) has a charge of Mn+4 because four electrons were removed from the atom.
When reduction occurs, the charge on the ion decreases. The more electrons gained, the smaller the charge on the ion. Using the manganese example from above, when Mn+4 is reduced by gaining two electrons, it becomes Mn+2. When Mn+2 is reduced again by gaining two more electrons, it becomes the manganese atom, Mn(s). Notice that the charge goes from +4 to +2 to 0 as the ion is reduced.
OXIDATION: Lost electrons are written on the PRODUCT side (to the right of the arrow).
REDUCTION: Gained electrons are written on the REACTANT side (to the left of the arrow).
Oxidation and reduction are PROCESSES, and substances (elements or compounds) are either REDUCING AGENTS or OXIDIZING AGENTS. Oxidizing agents oxidize other substances by accepting its electrons. Strong oxidizing agents: groups 16 & 17 (&15). Reducing agents reduce other substances by supplying electrons to the substance being reduced. Strong reducing agents: groups 1 & 2 (and 3-13).
Here is an EduCreate video giving you some examples to work with.
This is a link to some videos that walk you through oxidation numbers, redox reactions, and half-reactions.
A shortcut to remember this is: OIL RIG. (Oxidation Is Loss, Reduction Is Gain). Substances that are reduced are called oxidizing agents and substances that are oxidized are called reducing agents.
When substances are not ionic and it is harder to "see" where the electrons are going, you have to rely on electronegativity. In covalently bonded molecules, you have to look at the more electronegative of the elements (particularly groups 16 & 17). These elements have high electronegativities (ENs) because they don't want to lose the valence electrons they already have. The opposite holds true for groups 1 & 2; low ENs because they don't have a need to keep the valence electrons they already have.
Electronegativity Table (Source: www.mikeblaber.org)
The more electronegative atom is treated as if it is being reduced by gaining electrons from the other atom. The less electronegative atom is treated as if it is being oxidized by losing electrons to the other atom.
When oxidation occurs, the charge on the ion increases. The more electrons lost, the more positive the ion becomes. Manganese has two oxidation states (two types of ions). Manganese (II) has a charge of Mn+2 because two electrons were removed from the manganese atom, and manganese (IV) has a charge of Mn+4 because four electrons were removed from the atom.
When reduction occurs, the charge on the ion decreases. The more electrons gained, the smaller the charge on the ion. Using the manganese example from above, when Mn+4 is reduced by gaining two electrons, it becomes Mn+2. When Mn+2 is reduced again by gaining two more electrons, it becomes the manganese atom, Mn(s). Notice that the charge goes from +4 to +2 to 0 as the ion is reduced.
OXIDATION: Lost electrons are written on the PRODUCT side (to the right of the arrow).
REDUCTION: Gained electrons are written on the REACTANT side (to the left of the arrow).
Oxidation and reduction are PROCESSES, and substances (elements or compounds) are either REDUCING AGENTS or OXIDIZING AGENTS. Oxidizing agents oxidize other substances by accepting its electrons. Strong oxidizing agents: groups 16 & 17 (&15). Reducing agents reduce other substances by supplying electrons to the substance being reduced. Strong reducing agents: groups 1 & 2 (and 3-13).
Here is an EduCreate video giving you some examples to work with.
This is a link to some videos that walk you through oxidation numbers, redox reactions, and half-reactions.