Periodic Table of Chemical Elements

Basic Chemistry: The Periodic table of elements is a tabular arrangement of all known chemical elements, organized on the basis of their atomic numbers and internal configuration*, in the order of increasing electron number. Atomic number is a number of protons in the nucleus, electron configuration is the distribution (position) of electrons of an atom or molecule.

Internal Configuration

Recurring chemical properties: Elements in periodic table are presented in order of increasing atomic number, which is typically listed with the chemical symbol in each box. The standard form of the table consists of a grid of elements laid out in 18 columns and 7 rows, with a double row of elements below that did not fit standard table format - Lanthanoids and Actinoids.

This table format is generally attributed to a russian chemist Dmitri Mendeleev who in 1869 published the first widely recognized periodic table. He developed it to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to fill gaps in this table. Most of his predictions were proved correct when the elements in question were subsequently discovered. Mendeleev's periodic table has since been expanded and refined with the discovery of newer elements and the development of new theoretical models to explain chemical behavior.

Proof of Existence of Chemical Elements

Element Groups