Plz help me its the last question If an atom of Thulium, Tm, has a mass of 172 and ejects an alpha particle, what is the new mass and atomic number? What element does this atom belong to now?

¹⁶⁸₇₉Au

Explanation:

The symbol of the atom is given as;

          ¹⁷²₈₁Tl

If undergoes a nuclear reaction and it ejects an alpha particle;

 An alpha particle is the same as an helium atom

      ¹⁷²₈₁Tl  →  ₂⁴H   +     ₐᵇK

K is the hypothetical symbol of the new atom

b is the new mass number

a is the new atomic number;

 Conserving mass number;

        172  = 4 + b

        b  = 172  - 4  = 168

Conserving atomic number;

        81  = 2 + a

        81 - 2  = a

         a  = 79

The new compound is gold with a symbol of;

       ¹⁶⁸₇₉Au