Question
90Th234 emits 7alpha particles and 6 beta particles. What will be the atomic number and mass number of the resulting atom.
Solution
Loss of one alpha particle results in decrease in mass number by 4 units and decrease in atomic number by 2 units.
∴ Loss of 7 a particles will decrease the mass number by 7 x 4 = 28 units and atomic number by 7 x 2 = 14 units
Loss of beta particle increases atomic number by 1 and mass number remains same.
∴ Loss of 6 beta particles will increase atomic number by 6 units.
∴ Mass number of new element = 234 – 28 = 206
∴ Atomic number of new element = 90 – 14 + 6 = 82
