Page 181 - AFCAT-GK-GEF-protected
P. 181

WHATSAPP :- 8699247491
                   YOUTUBE CHANNEL :- GOVERNMENT EXAMS FUNDA

                              FACTS ABOUT PERIODIC TABLE




                   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.

                   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.
   176   177   178   179   180   181   182   183   184   185   186