vanadium has an atomic mass of 50.9415 amu. it has two common isotopes. one isotopes has a mass of 50.9440 amu and a relative abundance of 99.75%.

Average atomic mass of the vanadium = 50.9415 amu

Isotope (I) of vanadium' s abundance = 99.75 % = 0.9975

Atomic mass of Isotope (I) of vanadium, m = 50.9440 amu

Isotope (II) of vanadium' s abundance = (100% - 99.75 %) = 0.25 % = 0.0025

Atomic mass of Isotope (II) of vanadium, m' = ?

Average atomic mass of vanadium =

m * abundance of isotope (I) + m' * abundance of isotope (II)

50.9415 amu = 50.9440 amu * 0.9975 + m' * 0.0025

m' = 49.944 amu

The atomic mass of isotope (II) of vanadium is 49.944 amu.