February 23 - Plutonium Day

nPosted on February 23, 2020

Key Points

nA few radioactive elements are pretty famous:
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Radium – Atomic # 88 – the element discovered by Marie and Pierre Curie (and one of the big contributors to Marie Curie’s death!)
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Uranium – Atomic # 92 – probably the first radioactive element ever discovered, and the one used in the first nuclear weapon used in war
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nPlutonium – Atomic # 94 – first produced, isolated, and identified on this date in 1941, by Glenn T. Seaborg and a team of scientists at the University of California, Berkeley.
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nThe scientists produced plutonium by bombarding uranium with “heavy hydrogen” – the form of hydrogen that has one proton plus one neutron (rather than just a proton).
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nActually, when the scientists smashed heavy hydrogen into atoms of uranium in the particle accelerator, the first radioactive element that formed was NOT plutonium. Instead, neptunium was formed. Neptunium is Atomic #93.
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nThe atomic numbers I’ve been giving is the number of protons each element has. The number of protons is the essential factor that makes each element what it is. You can kind of see how scientists formed new elements by hurling a proton-neutron combination at it. With enough speed, the proton and neutron of the heavy hydrogen enters the nucleus of the uranium and then “sticks” – and now the element has one more proton and is no longer uranium! It’s neptunium.
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n In other words: U (92 protons)
n + heavy hydrogen (1 proton, 1 neutron)
n = Np (93 protons)
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nSo how does the neptunium turn into plutonium?
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nRemember, the scientists bombarded the uranium with a proton AND a neutron; the result (neptunium) is an unstable element that fairly quickly – and all on its own, while just sitting around – “decays” or changes into another element. This change is caused by the extra neutron releasing a beta particle and thus transforming into a proton.
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nOne extra proton changes the neptunium into plutonium!
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n In other words: Np (93 protons)
n 1 neutron – beta particle = + 1 protron
n = Pu (94 protons)
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nAll radioactive elements are unstable; all of them decay into other elements by releasing either particles or radiation. That’s what makes them radioactive! A chunk of iron or pile of sulphur that are just sitting around will never change into another element – that’s what makes them NOT radioactive.
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nBut there is a huge difference between how unstable different radioactive elements are. The thing we talk about to compare stability is an element’s “half life” – which is the approximate amount of time it takes for half of the atoms in a sample to decay (change into another element).
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nUranium is a relatively stable radioactive element. Its half life is about 4.5 BILLION years! It sticks around for a long, long time.
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nOne really unstable element is francium. It has a half life of just 22 minutes. That means that roughly half of the atoms of a sample of francium will have transformed into either radium or astatine in just 22 minutes! Meitnerium has a half life of just 4 or 5 seconds. It’s really, really unstable!
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nHow do the half lives of neptunium and plutonium compare to uranium, francium, and meitnerium? Take a peek:
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n U – 4 billion years
n Pu – 88 years
n Np – 2 days
n Fr – 22 minutes
n Mt – 4 seconds
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nBy the way, did you notice anything about these three element names:

uranium
n neptunium
n plutonium
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n?
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nUranium was named after the planet Uranus, which was discovered just a few years before the element was discovered and named.
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nWhen scientists were able to create new elements from uranium, they decided to name them after the planets Neptune and Pluto. Of course, since then Pluto got downgraded from “planet” to “dwarf planet.”
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