<span>Mass Number = (Atomic Number) + (Number of Neutrons) so you solve for the Number of Neutrons and you get:
Number of Neutrons = (Mass number) - (Atomic Number)
Mass Number equals protons plus neutrons, round atomic weight to nearest whole number
Atomic Number equals number of Protons</span>
Electrons travel around the nucleus in fixed energy levels with energies that vary from level to level
Atomic mass :
29.5 * 203 + 70.5 * 205 / 100 =
5988.5 + 14452.5 / 100 =
20441 / 100 = 204.41 u
atomic mass of Thallium <span>204.41 u
</span>
hope this helps!
