It took many tonnes of pitchblende to produce the tenth of a gram of radium that the Curies eventually extracted. It's classified in the periodic table as an alkaline earth metal - the heaviest of the ...

There are 118 elements in the periodic table, each with a unique symbol and atomic number. Symbol: A one or two-letter abbreviation used to represent the element. Atomic number: The number of ...

VOICEOVER: Chemical symbols and formulas. Every element in the periodic table is represented by a ... Scientist Marie Curie discovered two elements: radium and polonium. She discovered that ...