The International Year of the Periodic Table

The periodic table is one of the most significant achievements in science which captures the essence of chemistry, physics and biology. On the 20th of December 2017, the United Nations General Assembly proclaimed that 2019 will be the 150th anniversary of the periodic table and has therefore been named the ‘International Year of the Periodic Table of Chemical Elements’ (IYPT).

IYPT is a celebration of scientists, their members and their communities. It’s a way of working with their communities to engage people in the Royal Society of Chemistry (RSC) and the periodic table. The RSC are holding activities throughout 2019, including public lectures, teacher resources, public outreach, themed journals and books, and grants to fund IYPT activities and communities.

IYPT is an opportunity for us to develop new resources and raise awareness, to inspire people of all ages, experience and backgrounds. The Periodic Table of Elements is a great teaching tool and probably the most recognisable thing in chemistry.’ – The Royal Society of Chemistry.

What is the Periodic Table?

The periodic table is a table of the chemical elements that have been arranged in order of atomic number, usually in rows, so that elements with similar atomic structure appear in vertical columns. The periodic table is used as a tool for scientists to understand and predict the properties of all the elements.

In 1869, Russian scientist Dmitri Mendeleev discovered the periodic table of elements. At the time, only 63 of the 118 elements had been discovered, Mendeleev acknowledged this and left gaps in the table for elements yet to be discovered.

The elements discovered in the following years confirmed Mendeleev’s predictions of the undiscovered elements, revealing the brilliance of the periodic table. 55 elements have been discovered since his discovery, and all were added to the table according to their atomic mass. Mendeleev foresaw properties of some of these elements when attempting to order them, which explains why the Periodic Table was so successful and is still used today.

Element 101 was named mendelevium to honour Mendeleev’s contributions to science and the Periodic Table. This is a rare distinction, only 50 scientists have elements named after them.

The History of the Periodic Table of Chemical Elements

1669 – German amateur alchemist Hennig Brand created an object called the ‘Philosopher’s Stone’ that supposedly could turn metals into pure gold. Whilst heating residues of urine, some liquid dropped out and burst into flames. This was the first discovery of phosphorus.

1680 – Phosphorus became public after Robert Boyle also discovered it.

1809 – at least 47 elements were discovered, and scientists began to see patterns in the characteristics.

1863 – English Chemist John Newlands divided the 56 discovered elements into 11 groups based on these characteristics.

1869 – Dimitri Mendeleev, developed the periodic table.

1886 – French physicist Antoine Bequerel first discovered radioactivity.

          –  Ernest Rutherford named three types of radiation: alpha, beta and gamma rays.

          –  Marie and Pierre Curie started working on the radiation of uranium and thorium and later                                                                                         discovered radium and polonium. They also discovered that beta particles were negatively charged.

1894 – Sir William Ramsay and Lord Rayleigh discovered noble gases, known on the periodic table as group 0.

1897 – Electrons (small negatively charged particles in an atom) were first discovered by physicist J. J. Thomson.

          –  John Townsend and Robert Millikan determined their exact charge and mass.

1900 – Bequerel discovered that electrons and beta particles as identified by the Curies are the same thing.

1903 – Rutherford announced that radioactivity is caused by the breakdown of atoms.

1911 – Rutherford and German physicist Hans Geiger discovered that electrons orbit the nucleus of an atom.

1913 – It was discovered by Bohr that electrons move around a nucleus in discrete energy called orbitals. Radiation is emitted during movement from one orbital to another.

1914 – Rutherford first identified protons in the atomic nucleus. He also transmutated a nitrogen atom into an oxygen atom for the first time.

          – English physicist Henry Moseley provided atomic numbers, based on the number of electrons in an atom, rather than based on atomic mass.

1932 – Neutrons and isotopes were first identified by James Chadwick, completing the basis for the periodic table.

          – Cockroft and Walton first split an atom and changed it to two helium nuclei by bombarding lithium in a particle accelerator.


1945 – Glenn Seaborg identified lanthanides and actinides, which are usually placed below the periodic table.

In 2016, there were four undiscovered elements according to the gaps in the periodic table. The addition of nihonium, moscovium, tennessine and oganesson has classed the table as complete… for now!

Fun Facts about the Elements

  • Francium is the rarest element on earth, there is likely to be no more than a few ounces of it on earth at any given time.
  • The only letter not in the periodic table is the letter J.
  • Although there is helium on earth, it was first discovered by observing the sun.
  • The heaviest element on the periodic table is uranium with an atomic weight of 238.
  • With an atomic weight of 1, Hydrogen is the lightest among all the elements on the periodic table. That is the reason it is located on the left corner of the table.
  • The periodic table only has 2 liquids.

If you want to learn more about the periodic table, take a look at the Periodic Table Song!