Oxidation Number Electron Numbers Compounds State Neutral

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The oxidation state or oxidation number is defined as the sum of negative and positive charges in an atom, which indirectly indicates the number of electrons it has accepted or donated. The oxidation number is a convenient conceptual approximation when working with complex electrochemical reactions that eases the tracking of electrons and helps verify that they have been conserved. This is especially useful whilst expressing complex half-reaction equations involved in oxidation/ reduction reactions.

Atoms are defined as having an oxidation number of zero, meaning that they are electrically neutral. The positive protons in the nucleus balance the negative electron cloud surrounding it, there being equal numbers of both. If an atom donates an electron it has more protons than electrons and becomes positive. This ion is said to have an oxidation number of +1. Conversely if an atom accepts an electron it becomes negatively charged, gaining an oxidation number of -1. In summary, if an atom or ion donates an electron in a reaction its oxidation state is increased by one, if an element accepts an electron its oxidation state is decreased by one.

Oxidation numbers are denoted in chemical names by bracketed roman numerals placed immediately after the relevant element. For example, an iron ion, with an oxidation state of +3 is expressed as iron (III). Manganese with an oxidation state of +7 present in manganese oxide is given the name manganese (VII) oxide. The motive for placing oxidation numbers in names is only to distinguish between different compounds of the same elements. The actual charge (positive/negative) of the ion is not expressed because it is not necessary for this purpose.

In chemical formulae, the oxidation number of ions is placed in superscript after the element's symbol. For example, oxygen (-II) is written as O^2-. Oxidation numbers of neutral numbers are not expressed. The following formula describes the element I₂ accepting two electrons to gain an oxidation number of -1.

I₂ + 2e^- → 2I^-

When dealing with reactions, the following rules define oxidation number:

The atom with the greater Electronegativity of disimiliar atoms sharing an electron is counted as receiving the electron.
Identical atoms sharing an electron are each credited with one/half of the electron.

Sometimes it is not immediately obvious what the oxidation number of ions in a molecule are from its molecular formula. For example, given Cr(OH)₃, no oxidation numbers are present yet it is clear that ionic bonding is occurring.

There are a number of rules that can be used in determining an ion's oxidation number:

The oxidation number of (neutral) atoms equal zero.
In neutral molecules, the sum of the oxidation numbers adds up to zero.
Fluorine always has a -1 oxidation number within compounds.
Oxygen has an oxidation number of -2 in compounds, except (i) in the presence of fluorine, in which fluorine's oxidation number takes precedence; (ii) in oxygen-oxygen bonds, where one oxygen must neutralize the other's charge; (iii) in peroxide compounds, in which it takes an oxidation number of -1.
Group I ions have an oxidation number equal to +1 within compounds.
Group II ions have an oxidation number of +2 within compounds.
HalogenThe halogens are a chemical series. They are the elements in Group 17 (old-style: VII or VIIA) of the periodic table: fluorine, chlorine, bromine, iodine, and astatine. The word comes from Greek roots meaning "salt" and "creator". These elements are diatos, besides fluorine, generally have -1 oxidation numbers in compounds. This rule can be broken in the presence of oxygen or other halogens, where the oxidation numbers can be positive.
Hydrogenhydrogen helium H Li Full table General Name, Symbol, NumberHydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1 , s Density, Hardness 0. 0899 kg/m3, NA Appearance colorless Atomic properties Atomic weight 1. 00794 amu Atomic radius (ca always has an oxidation number of +1 oxidation number in compounds, except in metal hydrides where instead it is -1.

With the example, Cr(OH)₃, oxygen has an oxidation number of -2 (no fluorine, O-O bonds or peroxide present), and hydrogen has a state of +1 (not a metal hydride). So, the triple hydroxideHydroxide is a functional group consisting of oxygen and hydrogen: :-O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. Organic molecules containing a hydroxyl group has a charge of 3*(-2 + 1) = -3. As the compound is neutral, Cr has to have a charge of +3.

See also: ElectrochemistryElectrochemistry is the study of the electronic and electrical aspects of chemical reactions. The elements involved in an electrochemical reaction are characterized by the number of electrons each has. The oxidation state of an ion is the number of electr, valencyIn chemistry, valency is the power of an atom of an element to combine with other atoms measured by the number of electrons which an atom will give, take, or share to form a chemical compound. This is related to the number of spaces left in an atom's elec

Chemical properties

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