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The periodic table was constructed by scientists who noticed periodic trends in known elements of the time. Indeed, the patterns found in it is what gives the periodic table its power. Many of the chemical and physical differences between the 5th period (Rb–Xe) and the 6th period (Cs–Rn) arise from the larger relativistic effects for the latter. These relativistic effects are particularly large for gold and its neighbors platinum and mercury. An important quantum relativistic effect is the Van der Waals force.