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
Henry I kept lions, leopards and camels at Woodstock in the 12th century.
Quote of the Day
"Ἀνερρίφθω κύβος - let the die be cast
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~ Julius Caesar
On This Day
1846 Scottish surgeon Robert Liston was the first European to use anaesthesia during an amputation. He could amputate a leg in two and a half minutes.
1898 Scientists Pierre and Marie Curie discovered the radioactive element radium.
1937 'Snow White and the Seven Dwarfs', the world's first full-length animated film, premiered in the USA
1946 A tsunami caused by an undersea earthquake killed at least 1,362 and left thousands homeless in Japan.
1967 Louis Washkansky, the first man to undergo a heart transplant, died in Cape Town, South Africa, 18 days after his operation.
1988 Pan Am Flight 103 exploded as it was flying over Lockerbie, Scotland. All 243 passengers and 16 crew, and 11 residents of Lockerbie were killed