An isotope of an element has a slightly different number of particles to other isotopes of the element. So, the most common isotope of oxygen is oxygen-16, and it has 16 nucleons (both protons and neutrons) in its nucleus. Oxygen-18 has 18 nucleons.
Isotope
Fact of the Day
It is said that Henry VI banned low-cut blouses and dresses from court, in case he caught sight of a cleavage.
Quote of the Day
"This is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.
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~ Winston Churchill on the Battle of Egypt
On This Day
1189 Richard the Lionheart initiated the Third Crusade to reconquer the Holy Land from Saladin.
1549 Parliament passed the First Act of Uniformity, requiring the Book of Common Prayer to be used in all public church services.
1793 Louis XVI was executed in the Place de la Revolution in Paris, after being convicted of conspiracy with foreign powers.
1908 New York city made it illegal for women to smoke in public.
1911 The first Monte Carlo car rally was held. Seven days later it was won by Henri Rougier.
1924 Vladimir Lenin, architect of the Bolshevik Revolution and first leader of the Soviet Union, died of a brain hemorrhage.
1941 The Daily Worker, official newspaper of the UK communist party, was banned because of its views on World War II.
1950 George Orwell, author of 1984 and Animal Farm, died after a three year battle against tuberculosis.
1976 The first Concorde jets carrying commercial passengers simultaneously took off at 11:40am from London and Paris.
2008 Black Monday saw the FTSE 100's biggest ever one day fall. Euro markets had their worst result since 9/11 and Asia's fell 14%.