The Periodic Table is how scientists have organized the 100+ elements that make up all matter. It was proposed by Dmitri Mendeleev, a Russian chemist, in 1869.
Unlike previous attempts to organize the elements by characteristics, Mendeleev arranged them in order of the mass of their electrons. He also left blank spaces for items that had not yet been identified. As a result, he was able to predict the characteristics of those yet-to-be-discovered elements.
In the Periodic Table, the elements are grouped in two ways:
Periods: These move across the table from left to right. As we move in this direction, the number of protons in the atom’s nucleus increases by one.
Groups: A group is represented by each vertical column. Groups are made up of elements that share similar characteristics because they typically have the same number of electrons in their outer shell.