Periodic Table. The Periodic Table is a way of classifying elements. The elements in the periodic table are arranged horizontally, in increasing order of their atomic number. . Structure of the Periodic Table. The Vertical Column = GroupThe Horizontal Row = Periods. . The GROUP. A vertical column in the periodic table is called a group.There are 8 Groups : I, II, III, IV, V, VI, VII and VIII.Transition Metals are grouped between Group II and III. They have no group numbers..