The Periodic Table is one of the best ways of organizing the elements. The vertical columns are called groups, and the horizontal rows are called periods. The atoms in a group increase in size as you go down on the periodic table. And the atoms in the periods increase in the number of electrons and protons and they gain valence. The idea for the table was originally proposed by a Russian chemist named Dmitri Mendeleev in 1869. Since then, Dmitri's table has been expanded, refined and perfected over the years.
The Periodic Table of Elements
The Periodic Table is one of the best ways of organizing the elements. The vertical columns are called groups, and the horizontal rows are called periods. The atoms in a group increase in size as you go down on the periodic table. And the atoms in the periods increase in the number of electrons and protons and they gain valence. The idea for the table was originally proposed by a Russian chemist named Dmitri Mendeleev in 1869. Since then, Dmitri's table has been expanded, refined and perfected over the years.