What is used to define the location of the elements on the periodic table?

Expert Answers
gsenviro eNotes educator| Certified Educator

In the periodic table of the elements, the location of any element is defined by its group and period. A group is a column in the periodic table which contains the elements with same number of valence electrons. There are 18 groups in the periodic table. For example, group 18 belongs to the noble gases, elements with fully filled electron orbitals, that have 0 valence electrons. Similarly, group 2 is metals, known as alkaline earth metals, and contain 2 valence electrons. The periods are rows in the periodic table and each period consists of elements with the same number of electrons shells. There are 7 periods. For example, period 2 contains elements with only s and p orbitals, while period 1 contains elements with only s electron orbitals. 

Hope this helps.