How We Discovered Radioactivity and its Effects

Radioactivity was first witnessed in 1896 and can be extremely dangerous to living tissue. All matter is made up of tiny building blocks called atoms. An atom is made up of protons and neutrons at its centre (the nucleus) with electrons orbiting. Different combinations of these particles make up different elements. Some atoms are unstable (uranium and radium atoms, for example) and don’t have enough energy to keep themselves together. It’s because the atom’s nucleus has an odd number of protons or neutrons. As the decaying process occurs (or half-life), the unstable atom release alpha, beta or gamma rays making it radioactive.

Atom Model (The Tech Times)
Model of an Atom Credit: The Tech Times

The discovery of X-rays paved the way for radioactivity. Wilhelm Röntgen eventually became a professor but had a hard time after initially being expelled from university for a student prank. In 1895, the German scientist was experimenting with vacuum tubes and electrical currents. He covered half of his experiment with a screen to block out light and noticed strange rays reacting to the solution he was using. Not knowing what to call what he found, Röntgen nicknamed the phenomenon an X-ray (X meaning unknown) and the definition stuck. Röntgen conducted the first human X-ray later that year.

Röntgen and First X-ray (Ancient Pages)
Röntgen and the first X-ray Credit: Ancient Pages

Building on Röntgen’s theories, Henri Becquerel had his own ideas about X-rays. He came from a family of scientists with his father and grandfather having distinguished careers too. The French scientist hypothesised that X-rays would also be caused by prolonged exposure to the sun’s rays. In 1896, he had to delay his experiment due to bad weather. Coming back to the uranium salts he was using a couple of days later, he realised they too were giving off natural rays but ones different from X-rays. He brought his findings to the attention of his graduate student Marie Curie and her husband Pierre, another well respected scientist of the era. The three set about doing more research and experiments and concluded that Becquerel had discovered something entirely new. Marie was the one who came up with the term radioactivity. The three were awarded a Nobel Prize for their work.

Becquerel and the Curies (Chemistry LibreTexts)
From left: Becquerel, Pierre and Marie Credit: Chemistry LibreTexts

Marie and Pierre Curie continued investigating radioactivity and are largely remembered for their pioneering contributions in the field. Marie noticed the uranium samples they were using were contaminated with other radioactive substances. It took her four years to separate each of the elements and, in the process, she had discovered radium, thorium and polonium. She also developed a mobile X-ray machine that was widely used in World War I. She received a second Nobel Prize for her chemistry efforts later in life.

Ernest Rutherford and Machine (Ingenium)
Rutherford and an experiment Credit: Ingenium

Ernest Rutherford, a New Zealander-English physicist, is regarded as the Father of Nuclear Physics. He is responsible for categorising radioactive rays into their intensities. Alpha rays are at the lower end of the spectrum, beta rays are in the middle and gamma rays at the top. Alpha and beta rays can usually be stopped by a millimetre of foil while humans need around a metre of concrete for protection from gamma rays. In 1909, Rutherford used gold foil to deflect alpha particles and was able to work out the makeup of an atom. He refined his experiments and in 1919 used alpha particles to bombard oxygen atoms and turned them into nitrogen atoms. Newspapers at the time referred to his success as ‘splitting the atom’. He also discovered the proton and was awarded a Nobel Prize for his work.

When a person is exposed to a radioactive substance, they will suffer from radiation sickness. Radiation is a poison and attacks every cell in a body. In small exposures, a person will be uncomfortable and vomit until it passes, but they’ll have a greater chance of developing cancer later in life. Large doses are fatal and a person will experience painful burns all over their body, excessive bleeding, difficulty breathing, possible seizures and other effects.

Dial Painter (The Spectator)
Credit: The Spectator

From the 1910s to the 1940s, women worked in factories across the United States as dial painters. They used radium to paint analogue watch hands so they would glow in the dark. They had no protective clothing and would regularly put the brush tips in their mouths so they could apply the paint easier. It was suspected that radium was dangerous at the time, and because the women were only handling such small amounts, their employers believed there were no health risks. When it enters the body, radium acts like calcium and is attracted to bones. The effects were not immediate but over time, the Radium Girls felt tired, worn out and began to develop problems. Their bones, especially their jaws, began to rot away and tumours formed. Some started to die and the women became scared. They were also in agonising pain and sort justice. Over many years, the women were constantly rejected by lawyers because laws would need to be changed in order for them to gain anything. Their employers had been doing their own scientific research into prolonged radium exposure and had found a link between the substance and the women’s sickness. They decided to withhold the information because it would look bad for business. In two landmark cases of worker’s rights—one in 1928 and another in 1939—the Radium Girls won, were compensated, got laws changed and the effects of radium became known to the world. Sadly, they didn’t live long lives and suffered constantly.

Röntgen cared more for science and donated most of his money to his University until the end of his life. Becquerel worked up until his death in 1908, he was 55 years old. In 1906, Pierre Curie was crossing a road during a heavy rain storm and was killed instantly after being runover by a horse and carriage. Marie was given his class at Sorbonne University, making her the first woman in the institute’s history to hold such a position. She died from Aplastic anaemia in 1934, most likely caused by her years working closely with radioactive elements. In 1937, Rutherford died a few days after an operation to correct a hernia. In the century since radioactivity had been discovered, scientists now use specially designed attire and equipment when dealing with radioactive substances. It has greatly minimised health risks.

Uranium Ore (Cosmos Magazine)
Uranium ore Credit: Cosmos Magazine

This article was originally posted on the now defunct Science Niche website on December 23rd, 2018.


Discovery of Radioactivity (

Discovery of Radioactivity, The (

History of Radiation, The (

Radioactivity: Historical Figures (

What is radioactivity? (

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