A free radical is an atom or molecule that has an odd number of what?

More Questions:

Which US state's flag is the only one with a Union Jack on it?

What is the world's smallest country?

What US city's nicknames include "The Crescent City" and "The City that Care Forgot"?

What is used to measure horizontal and vertical angles in surveying?

What's the largest artery in the human body?

What number does the roman numeral LXXX denote?

In The Simpsons, what platoon was Abe Simpson in charge of during WWII?

Which dance classic did the group "The Trammps" bring us?

What alien comes from the planet Melmac?

Which Egyptian city was founded by Alexander the Great in 331 BC?

What does the seventh amendment of the US Constitution guarantee?

In what country was Che Guevara born?

In computer programming, which logic gate outputs TRUE if both inputs are TRUE?

Who created Popeye?

Which actor took the male lead in Hitchcock's film "The Birds"?