When lithium (Li) reacts with a proton (H+), two helium-4 nuclei (He-4) are formed. The reaction can be represented as follows:
3Li + 1H → 2He-4
In this reaction, the atomic number of lithium (Z = 3) combines with the atomic number of the proton (Z = 1) to form helium-4 nuclei, where the atomic number of helium-4 is 2.