How many neutrons does an element have if its atomic number is 47 and its mass number is 150?

Number of neutrons = atomic mass - atomic number

Number of neutrons = (150) - (47)

Number of neutrons = 103

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.