The periodic table was arranged by atomic mass, and this nearly always gives the same order as the atomic number. However, there were some exceptions (like iodine and tellurium, see above), which didn ...

Scientists use the periodic table to quickly refer to information about an element, like atomic mass and chemical symbol. The periodic table’s arrangement also allows scientists to discern trends in ...

The periodic table that we follow for our studies is the Modern Periodic Table, which is based on atomic number rather than atomic mass. This arrangement was established by the British physicist ...

This video is an interactive lesson in calculating an atom’s mass and atomic number. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells. The numbers of ...

The Periodic Table of Elements. Each entry contains the atomic number, chemical symbol, and atomic mass to two decimal places on elements where data is available. Undefined cells contain a space. Row ...

The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869: he formulated the periodic law as a dependence of chemical properties on atomic mass.