You'll find it on the wall of nearly every chemistry laboratory in the land. And generations of children have tried hard to memorise some of the 118 elements.
This year, the periodic table of chemical elements celebrates its 150th birthday. The United Nations has designated 2019 as the International Year of the Periodic Table to celebrate "one of the most significant achievements in science".
In March, it will be 150 years since the Russian scientist, Dmitri Mendeleev, took all of the known elements and arranged them into a table. Most of his ideas have stood the test of time, despite being conceived long before we knew much about the stuff that makes up the matter.
Mendeleev (1834-1907) created his early periodic table in 1869. He took the 63 known elements and arranged them into a table, mainly by their atomic mass. Although he wasn't the first to do this, his interpretation involved a leap of ingenuity, in that he put those with similar properties below each other into groups and left gaps for new elements to be slotted in.
After the discovery of protons, scientists realised that the atomic number of an element is the same as the number of protons in its nucleus. Thus, in the modern periodic table, the elements are arranged according to their atomic number - not their relative atomic mass.
There are now more than 100 elements, laid out in order of increasing atomic number. There are repeating patterns in the properties of the elements, which give the periodic table its name. Elements with similar properties are arranged to form columns. Currently, the seventh period of the periodic table has been completed, with the recent addition of four elements in December 2015.
This year, the periodic table of chemical elements celebrates its 150th birthday. The United Nations has designated 2019 as the International Year of the Periodic Table to celebrate "one of the most significant achievements in science".
In March, it will be 150 years since the Russian scientist, Dmitri Mendeleev, took all of the known elements and arranged them into a table. Most of his ideas have stood the test of time, despite being conceived long before we knew much about the stuff that makes up the matter.
Mendeleev (1834-1907) created his early periodic table in 1869. He took the 63 known elements and arranged them into a table, mainly by their atomic mass. Although he wasn't the first to do this, his interpretation involved a leap of ingenuity, in that he put those with similar properties below each other into groups and left gaps for new elements to be slotted in.
After the discovery of protons, scientists realised that the atomic number of an element is the same as the number of protons in its nucleus. Thus, in the modern periodic table, the elements are arranged according to their atomic number - not their relative atomic mass.
There are now more than 100 elements, laid out in order of increasing atomic number. There are repeating patterns in the properties of the elements, which give the periodic table its name. Elements with similar properties are arranged to form columns. Currently, the seventh period of the periodic table has been completed, with the recent addition of four elements in December 2015.
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