Valency is an ability of chemical elements to keep a certain amount of atoms of other elements. At the same time, this number of communications formed by this atom with other atoms. It is rather simple to determine valency.
Instruction
1. Note that the valency indicator is designated by the Roman figures and it is put over the sign of an element.
2. Pay attention: if the formula of the two-element writtensubstance that's right!, then, at multiplication of number of atoms of each element by its valency, at all an elementovdolzhna to turn out identical works.
3. Take into consideration that the valency of atoms of some elements is constant, and others - change, that is, has property to change. For example, hydrogen in all connections odnovalenten as forms only one communication. Oxygen is capable to form two communications, being at the same time bivalent. And here at sulfur the valency can be II, IV or VI. Everything depends on an element to which she unites. Thus, sulfur - an element with a variable valency.
4. Notice that in molecules of hydrogen connections it is very simple to calculate valency. Hydrogen always odnovalenten, and this indicator at the related element will equal to amount of atoms of hydrogen in this molecule. For example, in CaH2 calcium will be dvukhvalenten.
5. Remember the main rule of determination of valency: the work of an indicator of valency of atom of any element and amount of its atoms in any molecule is always equal to the work of an indicator of valency of atom of the second element and amount of its atoms in this molecule.
6. Look at the alphabetic formula designating this equality: V1 x K1 = V2 x K2 where V is a valency of atoms of elements, and To - amount of atoms in a molecule. With its help it is easy to define an indicator of valency of any element if other data are known.
7. Review an example with a SO2 sulfur oxide molecule. Oxygen in all connections dvukhvalenten, therefore, substituting values in a proportion: Vkisloroda x Oxygen = Vsery x Ksera, we receive: 2 x 2 = Vsery x 2. From here Vsery = 4/2 = 2. Thus, sulfur valency is equal in this molecule to 2.