Respuesta :
Mass of barium is 137.327 g/mol. Mass of radium is 226 g/mol.
Hence, radium has more mass therefore it will have the greatest density at STP.
Hope this helps :)
Answer:
Ra
Explanation:
Since density is directly proportional to mass and
Density=Mass/Volume
Atomic masses of Ba=137, Be=4, Mg=24, Ra=226
Hence Ra (radium) has the most density