Creation of energy by joining the nuclei of two hydrogen atoms to form helium.

Creation of energy by joining the nuclei of two hydrogen atoms to form helium.

• A. Mass number
• B. Fusion
• C. Fission
• D. Atomic number

Answer: (B)

Fusion is the process described: joining two light nuclei to form a heavier nucleus and releasing energy. When two hydrogen nuclei fuse to form helium, a small amount of mass is lost in the process and converted into energy, which is why this reaction releases energy. The energy comes from the binding energy difference; the resulting helium nucleus has a lower total mass than the sum of the two hydrogen masses, and that missing mass shows up as energy according to E = mc². This is what makes fusion such a powerful energy source, as seen in stars where extreme temperatures and pressures allow light nuclei to overcome their electric repulsion and fuse. This differs from fission, which splits a heavy nucleus into lighter ones, not joins them. The other terms—mass number and atomic number—refer to the count of nucleons or protons in a nucleus, not to the process of energy release through combining nuclei.

Fusion is the process described: joining two light nuclei to form a heavier nucleus and releasing energy. When two hydrogen nuclei fuse to form helium, a small amount of mass is lost in the process and converted into energy, which is why this reaction releases energy. The energy comes from the binding energy difference; the resulting helium nucleus has a lower total mass than the sum of the two hydrogen masses, and that missing mass shows up as energy according to E = mc². This is what makes fusion such a powerful energy source, as seen in stars where extreme temperatures and pressures allow light nuclei to overcome their electric repulsion and fuse.

This differs from fission, which splits a heavy nucleus into lighter ones, not joins them. The other terms—mass number and atomic number—refer to the count of nucleons or protons in a nucleus, not to the process of energy release through combining nuclei.