| The Periodic Table was created by Dmitry Mendeleyev, a Russian chemist and professor in 1869. |
| The Periodic Table has seven rows or periods. |
| The present Periodic Table has room only for 118 elements. The last element with atomic number of 118 is Oganesson |
| Lanthanides is a group of 15 elements from atomic number 57 to 71. Together with Scandium and Yttrium they are known as rare earth elements. |
| Rare earth elements which are 17 in number are actally not rare. Most of them are commonly found |
| Actinides is a group of 15 elements from atomic number 89 to 103. All actinides are radioactive. |
| The Periodic Table has 18 columns or groups. Some important groups are listed below. |
| Group 1 - Alkali metals or Lithium group consists of Lithium, Sodium, Potassium, Rubidium, Cesium and Francium. Hydrogen is not an alkali metal even though it is listed in the first column. |
| Group 2 - Alkaline earth metals or Beryllium group consists of Beryllium, Magnesium, Calcium, Strontium, Barium and Radium. |
| Group 15 - Pnictogens or Nitrogen group consists of Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth and Moscovium. |
| Group 16 - Chalcogens or Oxygen group consists of Oxygen, Sulphur, Selenium, Tellurium, Polonium and Livermorium. |
| Group 17 - Halogens or Flourine group consists of Flourine, Chlorine, Bromine, Iodine, Astatine and Tennessine. |
| Group 18 - Noble gases or Helium or Neon group consists of Helium, Neon, Argon, Krypton, Xenon, Radon and Oganesson. |