How Do You Calculate Valency?
The valency of an element measures its ability to combine with other elements. The valency is determined by the number of electrons in the outer shell of each atom of an element. All atoms with two or more electron shells are most stable when they have eight electrons in their outer shell, but only a few elements are naturally formed that way (neon, for example), and most that just have one or two electrons in their outer shell (lithium, for example) or six or seven (oxygen, for example) tend to react, or combine their outer-shell electrons with the outer-shell electrons of other adjacent elements to bond and form more stable multi-element molecules. Consult the periodic table of the elements to determine the valency of an element. The periodic table is organized by groups in rows and columns, and the elements of groups I-VIII have the same valency as others in their group. All the elements in group VIII have eight electrons in their outer shells, and thus have a valency of zero (highl