Promoting Science and Technology – Missions,Policies & Schemes

Periodic Table completes 150 years


From UPSC perspective, the following things are important:

Prelims level: Basic knowledge of the Periodic Table

Mains level: Not Much


  • The International Year of the Periodic Table of Chemical Elements was launched on January 29, 2019, at the headquarters of UNESCO in Paris.
  • The UNESCO stated that the events and activities will be held throughout the year in order to mark 150 years of the formation of the periodic table.
  • Dmitri Mendeleev was the man who published the periodic table for the first time in 1869.

The modern Periodic Table

  1. The periodic table is an arrangement of all the elements known to man in accordance with their increasing atomic number and recurring chemical properties.
  2. They are assorted in a tabular arrangement wherein a row is a period and a column is a group.
  3. Until 1863, the world was aware of only 56 known elements.
  4. The rate of scientific progress was such that every year, a new element was being discovered.
  5. It was during this time that Mendeleev came up with the idea of the Periodic Table.
  6. He published the Periodic Table in his book– The Relation between the Properties and Atomic Weights of the Elements.
  7. Mendeleev said that he arrived at the idea in his dream, where he saw all chemical elements falling into place on a table according to their chemical properties.
  8. Mendeleev had found a definitive pattern following which, each element could be placed according to their atomic weight.
  9. He had also predicted the qualities of the ‘missing’ (yet to be discovered) elements and gave them Sanskrit names.

Its Evolution

  1. The noble gases including helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) were added to the table between 1895 and 1901.
  2. Likewise, additions have been made to the periodic table as new elements have been discovered in the last hundred years
  3. In 1914, English physicist Henry Gwyn-Jeffries Moseley found out that each atomic nucleus can be assigned a number, according to the number of protons in that atom.
  4. This changed the way the periodic table worked. The table was redesigned according to the atomic number of elements rather than their atomic weight
  5. Rare-earth elements, including the elements in the Lanthanide series, were included in the atomic table in the late 19th century.

About the UNESCO event

  1. The year 2019 was declared as the International Year of the Periodic Table of Chemical Elements (IYPT 2019) at the 74th Plenary Meeting.
  2. The event will highlight the importance of periodic table in various science disciplines.
  3. Scientists and representatives of the private sector will came together for the event.

Aim of the International Year of Periodic Table of Chemical Elements

  1. The fundamental motto of IYPT 2019 is to recognize the importance of periodic table of chemical elements as one of the most important and influential achievements in modern science.
  2. The periodic table reflects the essence of all basic science disciplines like- physics, biology and chemistry.
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