TOEFL: A short history on the development and the importance of the periodic table.
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Now let's celebrate the elements. As many will remember from school chemistry lessons, the elements are all neatly set out in the periodic table - rhe brainchild of the Russian chemist Dimitri Mendeleev, who first drew it up 150 years ago. Our science correspondent Helen Briggs told me more about the periodic table and why it's special.
Chemists see this periodic table as a thing of beauty and also a thing of usefulness because by reading it you can understand the properties of different elements. But if you cast your mind back to the day of Mendeleev 150 years ago, there were only about 60 known elements. There are now more than 100.
And people have been trying to arrange them for some time. But he had this leap of ingenuity in that he arranged them in a table mainly by their atomic mass. But he put them in groups in terms of those with similar properties, and he left gaps for new elements to be slotted in. And this was before we knew anything about the structure of the atom and all of these things that we now know.
So it was an amazing development. He wasn't the first to do it but he had this leap of ingenuity. And the periodic table today, it has changed but it's still really the same basis from a 150 years ago.
And I looked at the periodic table when I was at school. My son is doing that at the moment. It's still used to teach millions of people across the world, isn't it?
That's right. Generations of schoolchildren have had to learn this periodic table and understand. And it's not really just about rote learning, it's about understanding what's the basis behind it.
And now we've got 118 elements, and they're arranged in these in groups. The vertical columns but also in period - so seven periods. So we've got now seven periods complete and there could be more.
That was Helen Briggs our science correspondent. And if you go to the UNESCO website, you can watch a whole lot of talks and debates about that periodic table including a lecture by Ben Bringa, the 2019 Nobel Prize winner in chemistry.