A French physicist named Henri Becquerel, in 1896, found that uranium emitted some unique kind of radiation without any input of energy. He called him Uranic rays.
This was a relatively new field and very less Scientists were working on it. Marie curie picked up this question for her Ph.D. and started working on it.
In her small laboratory she had a special (accurate) device to measure the radioactivity. It is called piezoelectric quartz electrometer; designed by her husband Pierre curie and his brother Jacob Curie.
Piezoeletric Quartz Meter
There are 3 instruments in the whole setup.
- Quadrant Electrometer
- Radioactive sample chamber
- Piezoelectric crystal
This crystal has a unique property. When pressure is applied to it’s opposite side, small electric charges are produced. In the experiment to find radioactivity, this had invaluable role along with Electrometer. The quicky she had to relive the pressure from crystal, more is the strength of element’s radioactivity.
She started testing many elements in the search if any other element showed the similar behaviour. After experimenting a lot, she finally found that thorium also had the capacity to ionize air i.e. emitted radiation.
She concluded, “The capacity of atoms to independently ionize air (by emitting energy) is not a feature of any one element, but it’s a property of matter.”
This took us a big step closer to the real understanding of matter.
One day she used Pitchblende (raw ore from which uranium was extracted) for her measurements. And Wola! She found that Pitchblende showed 4 times more radioactive than Uranium itself.
It gave a clear hint: There exists some new element (which we didn’t knew at that time) which is the reason behind increased radioactivity.
The Ultimate Goal was to find the New element.
Marie and Pierre curie ordered large Quantity of pitchblende and started working on that.
Knowing Chemical properties was the way to go.
One way to know more about new element is to by knowing its chemical properties. It’s chemical properties can help to Extract the Pure Metal. Curie tried different ways to treat it chemically, mix it, burn it, precipitate it, dried it and trying this again and again using different methodologies.
While making different solutions it was found that, not one, but two elements with different chemical properties to show radioactivity. Search was now for 2 new elements.
one element has its chemical properties close to Barium and other element’s properties is close to bismuth. (That new elements are now called polonium and Radium respectively.)
By july 1898, Marie and Pierre curie announced the discovery of new element and proposed the name “ polonium” for it. (Inspired from marie’s homeland: Poland)
Spectral Lines are check to element’s identity.
After preparing good enough solution, they took the sample to check its spectrum
Here’s the idea: Every element has its own set of spectral lines which cannot be changed by any means. Thus spectral lines are identity of an element.
And yes! Polonium showed a set of spectral lines never seen before and thus confirmed to be the new element.
“This is not enough” said Scientific Community
But spectroscopic evidence was not enough for scientific community to accept the discovery. They needed the real stuff. To measure its mass, other properties and place it correctly on Periodic table.
Curies have to extract the metal in its pure form.
They took out money from their own pocket and ordered pitchblende, the Raw ore. Large Quantites of it was required as radioactive element are present in trace quantities.
Marie Curie’s bold words: ” I can’t Give Up”
It took 4 years of extreme hardwork. Specially, radium was too difficult to isolate. For 4 years, marie curie continued to stir, sift, heat, cool, dissolve, precipitate and treat the radium bearing portions of the discarded ore.Oover this timeshe processed about 7 tons of slagfrom the mines largely by her own hands.
In august 1902, she finally managed to create a relatively pure sample of Radium Chloride, one – tenth of gram in mass.
Scientific community have to finally accept.
Marie curie received Nobel Prize in Chemistry,1911 for discovery for Radium and the study of nature and compounds of this remarkable element.
A scientist in his laboratory is not a mere technician: he is also a child confronting natural phenomena that impress him as though they were fairy tales. – Marie Curie