It’s Calcium hope that helps!
Hey there!:
Number of moles = ( number of atoms / 6.023*10²³ atoms )
given number of atoms = 5.03*10²⁴
Therefore:
Number of moles B = 5.03*10²⁴ / 6.023*10²³
Number of moles B = 8.35 moles
Hope that helps!
151.55 x 4 you have to add the molar masses for each element together.