150 years of the periodic table: Test your knowledge

[nitpicker]

https://www.bbc.com/news/science-environment-47008289

150 years of the periodic table: Test your knowledge

By Helen Briggs
BBC News

You'll find it on the wall of nearly every school chemistry laboratory in the land. And generations of children have sung the words, "hydrogen and helium, lithium, beryllium..." in an attempt to memorise some of the 118 elements. This year, the periodic table of chemical elements celebrates its 150th birthday.
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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 matter.
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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. "People had been doing that for some time - but finally there was some natural basis - or some law - that meant they needed to be arranged in some way," says Dr Wothers.

One hundred and fifty years on, there have been fundamental shifts in our understanding of matter. "Obviously Mendeleev at the time knew nothing about the sub atomic structure of the atom, so he was going on only the atomic weights, which weren't necessarily determined to the right accuracy at the time," says Dr Wothers.
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[stonecutter357]

1. my favorite youtube Ch is Periodic Videos !