February 10, 2012 - Happy Birthday, Per Teodor Cleve

He discovered some rare-earth elements.
He had a daughter who went on to be the first woman in Sweden to earn a doctoral degree in the sciences.
And he had a grandson who earned a Nobel Prize in Physiology!

Per Teodor Cleve was a Swedish chemist and geologist who was born on this date in 1840. As he studied rocks and minerals, he tried to figure out what elements made them up.

An earlier scientist, Carl Mosander, had discovered that a mineral called cerite was made up of the elements cerium, lanthanum, and didymium. The latter two elements were Mosander's discoveries, and so he got to name them. Lanthanum and didymium were entered into the Periodic Table of Elements of the day, and given appropriate abbreviations (La and Di). But...it turned out that Mosander was wrong about didymium being an element.

Cleve was able to prove that didymium could be broken down into two different elements. Later scientists were able to separate the salts of the two new elements, which are named neodymium (“new” dymium) and praseodymium (“green” dymium).

This is not an embarrassing chapter of science! This story does not prove that Mosander was a careless or ignorant scientist! He did the best he could with the equipment he had, and he made many discoveries that still stand today, including three elements. Instead of being an embarrassing chapter of science, this is a great story—it shows, once again, that science is self-correcting, that later discoveries often refine older discoveries, and that scientists are able to reach new heights of understanding partly because they are figuratively standing on the shoulders of great scientists of the past!

Our birthday boy, Cleve, also discovered two more new rare-earth elements: holmium and thulium.

Also on this date:


  1. Wow, incredible blog layout! How lengthy have you been running a blog for? you made running a blog look easy. The overall look of your site is magnificent, let alone as} the content material!
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  2. NEAT!
    I didn't know about either of these things!
    I love the idea of including "And On This Day in History..." kind of thing on the blog!

    Do you mind if I join you in that???

  3. I don't mind a bit, naturally! There are lots of lists of "on this day in history" -- but I try to be a bit different and include a paragraph or two about the events or birthdays that I highlight. And of course, I choose to focus on the details that interest me. I sure would love any links from your blog back to mine!!!