January 11, 2010

Francium discovered – 1939

The element francium was discovered by French chemist Marguerite Catherine Perey on this date in 1939. She had been analyzing another element, actinium, which experiences radioactive decay. In other words, without any outside force, actinium suddenly releases radiation or a particle—and becomes another element! Perey's sample of actinium became astatine, bismuth, and then francium.

too, is radioactive and experiences this kind of spontaneous decay, becoming astatine, radium, or radon. Radioactive elements are dangerous because of the radiation and high-energy particles they release.

Each radioactive element has its own half-life, which is a measure of how soon it decays into another element. (Half-life means, as you might guess, that half of a given sample has decayed in the time period.) Some radioactive elements have long half-lives. Uranium 234, for example, has a half-life of 240,000 years. But Francium is very unstable, with a half-life of only 22 minutes.

As a matter of fact, francium is the most unstable of all the elements that occurs in nature. Scientists estimate that there is no more than one ounce of francium in all of the earth's crust at one time. That makes it the second rarest naturally-occurring element!

Since Perey discovered the element, she got to name it. Francium was her second sugg
estion and honors France as the place of discovery. (Her first suggestion was catium, because Perey believed this new discovery would be the most electropositive cation of all the elements. Her supervisor didn't like the idea and pointed out that people would think of cat rather than cation.)

Last to be discovered...now on to creating new elements!

Perey's discovery of francium was the last discovery of a naturally-occuring element. But scientists have created (or synthesized) other elements in nuclear reactors and particle colliders. (A few of these elements have actually been discovered in tiny amounts, in nature, after first being synthesized.)

Some of these elements have been named after the place in which they
were created, following Perey's example of naming her discovery after her country. So many of the elements were first created in America, scientists started to run out of place names. Look at this list:
Americium – created in 1944, at the University of Chicago, U.S. of America
Berkelium – created in 1949, at the University of California, Berkeley

Californium – created in 1950, at the University of California, Berkeley

Lawrencium – created in 1961, at the University of California, Berkeley, Lawrence Radiation Lab

Other elements were named after famous scientists (although not the scientists who created them!).
Who is each of these elements named for?




ANSWERS: 1.Marie and Pierre
Curie 2. Albert Einstein 3. Enrico Fermi 4. Dimitri Mendeleev 5. Alfred Nobel

You can explore the periodic table of elements here.

Here is a game that can help you learn the Atomic Symbols of each element.

This visual periodic table loads somewhat slowly for me but is beautiful, with pictures and movies and lots of info (click around, of course!). I loved the Periodic Landscapes.

Now, for some common stuff...

Francium is a heavy, unstable, extremely rare element. But all around us are lighter, stable, common elements. Can you match the element name with the description?







8. Aluminum

A. Atomic number 1 – the simplest, lightest, most common element in the universe

B. Atomic number 2 – used inside lighter-than-air toys, it's safe because it doesn't react to other elements

C. Atomic number 6 – the building block of life because it forms chains and rings easily

D. Atomic number 7 – most of the air we breathe is made of this

E. Atomic number 8 – something plants get rid of, but that animals and fires need

F. Atomic number 13 – a lightweight, silvery metal

G. Atomic number 17 – a poisonous gas that, when mixed with a particular poisonous metal, makes yummy salt!

H. Atomic number 79 – a heavy yellow metal

ANSWERS: 1.C 2.E 3.B 4.D 5.H 6.A 7.G 8.F

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