‘A quick overview of the modern periodic table’ explains the arrangement of elements in the periodic table, and introduces the concept of periodic law. Elements were originally ordered by their equivalent weight, but this was superseded by atomic weight, and then atomic number. There are many versions of the periodic table, but all obey periodic law, which states that after certain regular, but varying intervals, the chemical elements show an approximate repetition in their properties. Developments in physics, especially quantum mechanics and relativity, have changed the way we think about elements and periodicity. The number of known elements has increased to 118 as the result of the synthesis of artificial elements.