The following statement represents a nuclear reaction - Scottish Highers Physics - Question 8 - 2017

To find nucleus Z in the reaction, we need to balance the reaction in terms of atomic mass and atomic number. The expression can be detailed as follows:

1. The initial nucleus is Lawrencium ( $^{256}_{103}Lr)$ with atomic number 103 and mass number 256.
2. Helium ($^{4}_{2}He)$ has an atomic number of 2 and a mass number of 4.
3. Let’s denote the unknown nucleus Z as having an atomic mass number A and atomic number Z.

The balance equation will be:

• Mass numbers: $256 = A + 4$
  Therefore, $A = 256 - 4 = 252$.

• Atomic numbers: $103 = Z + 2$
  This gives $Z = 103 - 2 = 101$.

4. Based on these values, nucleus Z must have an atomic number of 101 and a mass number of 252, which corresponds to the isotope $^{252}_{101}Md$.