<P> In chemistry , a group ( also known as a family ) is a column of elements in the periodic table of the chemical elements . There are 18 numbered groups in the periodic table , and the f - block columns ( between groups 3 and 4 ) are not numbered . The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms ( i.e. , the same core charge ) , as most chemical properties are dominated by the orbital location of the outermost electron . There are three systems of group numbering . The modern numbering group 1 to group 18 is recommended by the International Union of Pure and Applied Chemistry ( IUPAC ) . It replaces two older naming schemes that were mutually confusing . Also , groups may be identified by their topmost element or have a specific name . For example , group 16 is variously described as the oxygen group and as chalcogens . </P>
<P> In chemistry , a group ( also known as a family ) is a column of elements in the periodic table of the chemical elements . There are 18 numbered groups in the periodic table , and the f - block columns ( between groups 3 and 4 ) are not numbered . The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms ( i.e. , the same core charge ) , as most chemical properties are dominated by the orbital location of the outermost electron . There are three systems of group numbering . The modern numbering group 1 to group 18 is recommended by the International Union of Pure and Applied Chemistry ( IUPAC ) . It replaces two older naming schemes that were mutually confusing . Also , groups may be identified by their topmost element or have a specific name . For example , group 16 is variously described as the oxygen group and as chalcogens . </P>
what is the same within each group on the periodic table
what is the same within each group on the periodic table
core charge
core charge