Showing posts with label radioactivity. Show all posts
Showing posts with label radioactivity. Show all posts

November 7 - Happy Birthday, Marie Curie and Lise Meitner

 Posted on November 7, 2021


This is an update of my post published on November 7, 2010:




Two different eminent female scientists who did important pioneering work in the field of radioactivity were born on this day. Curie was born Maria Skłodowska in 1867, in Warsaw, Poland (at the time Warsaw was part of the Russian empire); most of her adult life and work were in France. Meitner was born in Austria in 1878, and (because she was Jewish) she later had to flee from the Nazis and ended up in Sweden.


Curie and her husband Pierre did experiments on uranium minerals and discovered two new elements, polonium and radium. Curie won two different Nobel prizes for her work (in Physics and Chemistry)—the first person in the world ever to win two, and still the only woman to win in two different fields. She coined the word radioactivity, invented techniques for isolating radioactive isotopes, and even did the world's first studies on radiation treatment of cancer. Sadly, she died from radiation poisoning.

The chemical element curium (atomic number 96) is named for Marie and Pierre Curie.
Radioactive decay

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Meitner and her colleague Otto Hahn discovered nuclear fission. Although Hahn received a Nobel prize for the discovery, Meitner was overlooked—an omission that many people think is terrible. Meitner and Hahn's work explained why fission released energy, exactly how uranium breaks down into lighter elements, and why no stable elements heavier than uranium exist in nature.

The element meitnerium (atomic number 109) is named for Meitner.
Fission is one of the things that are used in nuclear power
and nuclear weapons.



Learn about nuclear physics!

Atoms are basically made up of heavy particles called protons and neutrons, which are found in the center (or nucleus) of the atom, and a surrounding cloud of teensy, almost weightless particles called electrons. A particular element is defined as having a certain atomic number, which is the number of protons that element has.


Lithium is atomic number 3.
It has 3 protons,
and it usually has 4 neutrons
and 3 electrons.

Note that this is a diagram meant
to give information - it is not what
an atom "looks like."

If an atom of a particular element loses or gains an electron or two, it is called an ion.
Lithium is quite prone to losing an electron.
Note that, in this diagram, the protons and 
neutrons are not visible - they are represented
as a single spherical nucleus.


If an atom of a particular element has more or fewer neutrons than usual, it is called an isotope.


There are two naturally occurring isotopes of
lithium. Much more common is the lithium that
has 3 protons and 4 neutrons - each of which
are considered to weigh 1 in atomic weight; so
the most common lithium has an atomic weight of
roughly 7. Some lithium, however, has 3 protons
and only 3 neutrons; its atomic weight is
roughly 6. These isotopes of lithium are called
lithium 7 and lithium 6.

But if an atom of a particular element loses or gains a proton—it becomes another element!
If lithium were to somehow lose a proton, it would become
helium (which has 2 protons), above.

If lithium were to somehow gain a proton, it would become
beryllium (which has 4 protons), below.



  • Check out this wall chart. Click on sections to see the details and read the text!  Then use the online teacher's guide to the wall chart to find out more. 





 


Also on this date:


















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January 11 - Anniversary of the Discovery of Francium

 Posted on January 11, 2021

This post is an update of my January 11, 2010, post:

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.




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 suggestion and honors France as the place of discovery.
(Her first suggestion was catium, because Perey believed this new discovery would be the most electrically positive ion - or cation - of all the elements. Her supervisor didn't like the name suggestion 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, USA
Californium – created in 1950, at the University of California, Berkeley, USA
Lawrencium – created in 1961, at the University of California, Berkeley, USA, in the 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?
1. Curium
2. Einsteinium
3. Fermium
4. Mendelevium
5. Nobelium


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 is beautiful, with pictures and videos and lots of info (click around, of course!).

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?

1. Carbon
2. Oxygen
3. Helium
4. Nitrogen
5. Gold
6. Hydrogen
7. Chlorine
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 also 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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