On the periodic table the seven horizontal rows are called periods. On the left-hand side of the periodic table the row numbers are given as one through seven. The Periodic Table I History Ii Arrangement Of Elements Iii Periodic Trends Ppt Download Atomic number increases as you move down a group or across a period. . What is horizontal relationship in periodic table. The periodic table is divided into rows and columns. For instance hydrogen and helium are in the first period so they both have electrons in one orbital. Elements are arranged in order of increasing atomic number their physical and chemical properties show a periodic pattern. The horizontal rows in a periodic table are called group. Each period contains more elements than the previous one. The horizontal rows in the peiodic table are called periods. What do all the elements in a vertical column of the periodic table have in common. Moving acr...