What is the value of so4


Valence, valence, one for the stoichiometry of chem. Connections and reactions are a decisive parameter that is defined differently depending on the application. The term W. originally characterized the ability of a given atom to form a bond with a certain number of other atoms. In the course of time, the term has been expanded, today the following basic valence theoretical terms are included:

1) The stoichiometric W. of an element is a number zwhich indicates how many atoms or groups of atoms recognized as monovalent can bind an atom of the element in question or replace it in compounds. In binary compounds, the value sum (i.e. the product z · ν from stoichiometric value and stoichiometric number ν) of one binding partner equal to that of the other, i.e. that is, there can be no "free" valences in stable connections. This results in the possibility of calculating that of the other if the composition of a compound and the W. of one element are known. Hydrogen and fluorine are always monovalent. Accordingly, the elements Na, O, B, Si and S in the compounds are NaH, H2O, BF3, SiF4 and SF6 one-, two-, three-, four- or six-valued. The stoichiometric W. is not a constant for most elements, but can have different values. So is z. B. for nitrogen in the oxides N2O, NO, N2O3, NO2 and N2O5zN = 1, 2, 3, 4 or 5. The W. can only ever be an integer. In their formal calculation for iron in Fe3O4 it turns out however zFe = 8/3. This value must be interpreted in such a way that one Fe atom in the compound is divalent, while the other two are trivalent. In the same way as it is for an atom z also defined for a group of atoms: From the formulas NaOH, H2SO4, H3PO4 and NH4Cl result for the respective atom groups zOH = 1, zSO4 = 2, zPO4 = 3 and zNH4 = 1.

The stoichiometric value of a compound cannot be derived unambiguously from its formula, but rather results in relation to certain reactions and from the corresponding reaction equations. So the W. of acids and bases follows from the number of protons given up or taken up in an acid-base reaction. According to the reaction equation 2 NaOH + H2SO4 → Well2SO4 + H2O reacts NaOH as a monovalent base and H2SO4 as a dibasic acid. In the case of oxidizing and reducing agents, the W. results from the number of electrons taken up or released: In the reaction 5 Fe2+ + MnO4- + 8 H.+ → 5 feet3+ + Mn2+ + 4 H.2O the iron (II) ion is a monovalent reducing agent and the permanganate ion is a pentavalent oxidizing agent. The W. of a compound is by no means always fixed, but often depends crucially on the reaction conditions. It determines the size of the corresponding equivalent.

2) The Ionic valence (Ionic charge, Charge number) indicates the number of charges of an ion; it is indicated by superscript digits followed by a plus or minus sign (e.g. Ag+, NH4+, Cl-, SO42-).

3) The Cohesion (Bond value) indicates the number of atomic bonds in which an atom is involved in a compound (chemical bond).

4) The Oxidation number indicates which ion charge an element would have in a compound if it were made up of atomic ions. It is written with a preceding sign over the element symbol in the corresponding formula (e.g.