The Periodic Table of Elements turns 150 years old

While it may not seem possible, you can find every element known in the universe gathered together in one place. Chemists and chemistry students have been visiting it for years. And you can too! That place is the Periodic Table of the Elements, one of the most remarkable tools known to science, and this year it turns 150 years old.

Everything on earth and in the universe contains the atoms of at least one element, a substance made up of its own unique atom that cannot be broken down into any other substance.

The Periodic Table of the Elements lists all the known elements, grouping together those with similar properties. In effect, it summarizes the entire science of chemistry with squares containing symbols and numbers, much like scrabble tiles, arranged into rows and columns. 

The first Periodic Table of the Elements was constructed in 1869 by a Russian chemist named Dmitri Mendeleev. Mendeleev wrote the properties of the 63 elements known at the time on pieces of paper and arranged them in vertical columns in order of atomic weight, and horizontal rows of similar properties.

As Mendeleev arranged his tiles his periodic table became more than a record of known science. It became a predictor of future discovery. By looking at where an element appeared on the chart Mendeleev could correctly describe the properties of that element. Even more amazing was that where Mendeleev found gaps in his chart he could predict the properties of the element that would fit there. Even though they were yet to be discovered! 

Fast forward 150 years and there are now 118 confirmed elements in the periodic table. Today’s table also differs from Mendeleev’s in that elements are ordered according to atomic number rather than atomic weight.  Hydrogen, represented by the symbol H, is the lightest element and has an atomic number 1. This is why it appears in the top left corner of the periodic table. Oganesson (Og), created in 2002, is the heaviest and sits at the bottom right corner. 

While 90 of the elements in today’s periodic table are found in nature, scientists have created the rest. Technetium was the first man-made element.

Chemistry students and scientists no longer have to memorize facts and figures. They can tell by a glance at the periodic table whether an element is likely to conduct electricity, how solid it is or how it may react to other elements.  Elements in the first column, for example, are the alkali metals, which usually carry a +1 charge in reactions, will react vigorously with water and combine readily with nonmetals. The very last column of the table contains helium (He), neon (Ne), argon, (Ar), krypton (Kr), xenon (Xe) and radon (Rn). Collectively called the noble gases they are highly unreactive with other elements.

Dmitri Mendeleev never received the Nobel Prize for his discovery but was honoured with an even more rare reward. Element 101 was named Mendelevium, after him.

Most of the elements are metals which are shiny and are good at conducting electricity. Some common examples of metals are copper, silver, gold and aluminum which are solid at room temperature. Mercury is the only metal that takes liquid form at room temperature.

Article originally published in Brainspace Magazine Fall 2019

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