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Properties of Variable Valency

Valency is the measure of the reactivity of an element. This is the property of giving up or receiving electrons from the outermost electron shells of an element in connection with another element to make a compound. Variable valency is a type of valency in which the element can give up or receive a different number of electrons. This variability means some compounds have the same elements but with different properties and different chemical names. The elements with variable valency have a few properties in common.

Transition Metals and Non-metals
- The transition metals are the elements in groups, which are the vertical columns, three through 12, on the periodic table of elements. There are 38 total elements in this group. All of the transition metals except silver and zinc demonstrate variable valency. Transition metals are not the only elements to display variable valence. Certain non-metal elements will also demonstrate variable valency including oxygen and nitrogen.
Electrons and Charge
- The valence electrons are the electrons on the outermost shell of an atom. Transition metals give these electrons up to another element to have a complete electron shell, similar to the noble gases. Transition metals that display variable valence may give up additional electrons from the penultimate shell, which is the next to last electron shell of the element. This leads to a different charge. The more electrons the atom gives up, the larger its charge. For example, iron has two valencies, II and III. Iron II has a positive charge of two and iron III has a positive charge of three.
Names
- Transition metals that display variable valency may have different names associated with the different electron charges. For example, iron, which has the chemical notation Fe, has two valence variables, II and III. These are also called ferrous and ferric iron. Ferrous iron is iron that has a positive charge of two. Ferric iron has a positive three charge. Other common elements that have different name for the variable valency include copper and manganese.
Physical Properties
- The physical properties of an element that displays variable valence is significant, even when it is reacting with the same element. For example, Fe2O3 and FeO use the two difference valencies of iron. Fe2O3 is the ferric form of iron and this compound is magnetic. FeO uses ferrous iron and is not magnetic. The oxygen in these compounds has the same valence of negative two. An example of oxygen demonstrating variable valence is H2O and H2O2. H2O is water and is necessary for life. Oxygen in H2O show a valence of negative 2. However H2O2, which hydrogen peroxide, is a highly acidic compound and not safe to drink. Oxygen in H2O2 displays a valency of negative one in this compound.

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