No, RA is not a valid Scrabble word.
the sun god, the supreme Egyptian deity, worshipped as the creator of all life and typically portrayed with a falcon's head bearing the solar disc. From earliest times he was associated with the pharaoh
Synonyms: star
the chemical element radium
the chemical element of atomic number 88, a rare radioactive metal of the alkaline earth series. It was formerly used as a source of radiation for radiotherapy