Answer: In a full cycle of proton proton chain reaction, a helium nucleus is formed by the four hydrogen nuclei and a huge amount of energy nearly 0.7 percent of the original mass is lost.
Explanation: The Sun gets its energy when hydrogen nuclei are fused together to form helium nuclei within the solar core. This hydrogen burning is described by a sequence of nuclear fusion reactions called the proton-proton chain. Overall, this chain successively fuses four protons together to make one helium nucleus.