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.
Fact of the Day
Between April 1669 and the end of 1684, Charles II touched a total of 28,983 people (about 1,800 p.a.) for the King's Evil.
Quote of the Day
"Total abstinence is so excellent a thing that it cannot be carried to too great an extent. In my passion for it I even carry it so far as to totally abstain from total abstinence itself. "
~ Mark Twain
On This Day
41 Claudius was proclaimed Roman Emperor by the Praetorian Guard.
1327 Edward II was deposed by his wife, Isabella, and her lover, Roger Mortimer. They replaced him with his 10 year old son, Edward III, and for three years they ruled through him.
1533 King Henry VIII secretly married the newly-pregnant Anne Boleyn, even though he was still married to Catherine of Aragon.
1554 Thomas Wyatt gathered 4000 men in Kent, starting the Wyatt Rebellion against Queen Mary and her choice of Spanish husband.
1627 Father of modern chemistry, Robert Boyle, was born in Lismore, County Waterford, Ireland.
1942 Thailand declared war on the United States and Britain following intensive bombing by the Allies.
1945 The German offensive campaign in the Ardennes, which came to be known as the Battle of the Bulge, ended in Allied victory.