This is the same type of reaction as in Problem 1. 21H has one proton and one neutron. It loses the neutron, to become 11H, the common hydrogen nucleus that consists of one proton alone. The neutron is transferred to calcium-42 (20 protons and 22 neutrons), as you see from the Nuclear Table, making it calcium-43, 4320Ca.
Here the hydrogen remains hydrogen and the calcium remains calcium because the proton numbers don't change. The proton numbers determine what the chemical element is.