Example of Valencia Quimica

The Chemical Valencia is a number, positive or negative, that indicates how many electrons the atom can "give up" or "receive" of a Chemical Element in a Chemical Reaction, to join others in a bond.

The Chemical Valencia will depend on the Electronic configuration (the arrangement of the electrons) of the atom, being defined by those that remain in the outer shell.

Octet rule

Before establishing how valence is handled, it is necessary to understand the Octet rule.

The Rule of the Octet indicates that “An atom reaches stability when it becomes Eight Electrons in its last shell, Thanks to the formation of a link with one or more atoms ”.

Meaning of Valencia

To better detail Valencia, it is required to list the established rules:

Yes there are 1 electron in the last layer, the valence is +1, because the atom can be detach from 1 negative electron charge, becoming positive by a value of 1.

Yes there are 2 electrons in the last layer, the valence is +2, because the atom can be detach from 2 negative electron charges, becoming positive by a value of 2.

Yes there are 3 electrons in the last layer, the valence is +3, because the atom can be detach from 3 negative electron charges, becoming positive by a value of 3.

Yes there are 4 electrons in the last layer, the valence is +4 ó -4, because the atom is can detach from 4 negative electron charges, becoming positive by a value of 4, or it can equally receive 4 negative electron charges, becoming negative by a value of 4.

Yes there are 5 electrons in the last layer, the valence is -3, because to achieve the Rule of the Octet, the atom requires be accompanied by 3 negative electron charges.

Yes there are 6 electrons in the last layer, the valence is -2, because to achieve the Rule of the Octet, the atom requires be accompanied by 2 negative electron charges.

Yes there are 7 electrons in the last layer, the valence is -1, because to achieve the Rule of the Octet, the atom requires be accompanied by 1 negative electron charge.

Yes there are 8 electrons in the last layer, the valence is 0, that is, the atom is stable, because it does not need electrons to reach the Rule of the Octet. This valence corresponds to the atoms of the Noble Gases, which do not react normally with the atoms of other elements. For the latter they are also called inert gases.

Single Valencias and Multiple Valencias

The Periodic Table of Chemical Elements indicates which valence each atom carries. But as you can see, there are atoms that present not one, but several different valences due to the behavior of their shells or orbitals, which are sometimes in hybridization and present the surface electrons in different number.

Within the A groups, unique valences are usually handled, for example:

Lithium: +1, Sodium: +1, Potassium: +1, Calcium: +2, Magnesium: +2, Strontium: +2, Aluminum: +3, Silicon: 4, Chlorine: -1, Bromine: -1, Oxygen: -two.

But there are elements in these same groups that handle two or more valences:

Tin: +2,+4; Lead: +2, +4, Sulfur: -2, +4, +6.

In the case of Sulfur, which has 6 electrons in its last shell, -2 is mentioned for when it behaves receiving 2 negative charges; in addition +6 is mentioned, because it comes to combine giving up its 6 electrons.

Among the transition metals, they handle from 2 to multiple valences:

Chrome: +2, +3, +4, +6; Manganese: +2, +3, +4, +6, +7.

Valencia or State of Oxidation

The Valencia of Chemical Elements can change in the course of a Chemical Reaction, when substances are transformed. For example:

2KMnO₄ + 5H₂SW₃ -> K₂SW₄ + 2MnSO₄ + H₂SW₄ + 3H₂OR

In the Reagents, Manganese (Mn) behaves with Valencia +7 in Potassium Permanganate (KMnO₄). And when the reaction occurs, Manganese Sulfate (MnSO₄), in which Manganese has a Valencia of +2.

The Chemical Equation, then, represents a REDOX Reaction, in which the Manganese has been Reduced from a value +7 to a value +2. It is also important to identify the element that has been Oxidized, which in this case is Sulfur (S), which passes from a valence of +4 in Sulfurous Acid (H₂SW₃) at a valence of +6 in Sulfuric Acid (H₂SW₄).

It is for this type of Reactions that Valencia is also given the name of Oxidation state.

Examples of Valencia Chemistry

Lithium: +1

Sodium: +1

Potassium: +1

Calcium: +2

Magnesium: +2

Strontium: +2

Aluminum: +3

Silicon: 4

Chlorine: -1

Bromine: -1

Oxygen: -2

Tin: +2,+4

Lead: +2, +4

Sulfur: -2, +4, +6

Chrome: +2, +3, +4, +6

Manganese: +2, +3, +4, +6, +7