This topic accounts for approximately 6% of your exam marks.
stable
Low
Stable6%
Chain reactions, conditions for fusion and energy release compared between fission and fusion.
What "nuclear energy" means
An atomic nucleus contains an enormous amount of stored energy, held in place by the strong nuclear force that binds protons and neutrons together
Any time the arrangement of nucleons in a nucleus changes (by splitting it apart, joining nuclei together, or letting a nucleus decay), some of that stored energy is released
The three ways to release energy from the nucleus are:
Nuclear fission: one large unstable nucleus splits into two smaller nuclei
Nuclear fusion: two light nuclei join to form one heavier nucleus
Radioactive decay: an unstable nucleus emits an alpha, beta or gamma particle and changes into another nucleus (covered in topics 19 and 20)
The amounts of energy involved per reaction are millions of times larger than for chemical reactions (combustion, batteries, food). Burning a single hydrogen atom in oxygen releases about 10⁻¹⁸ J; fusing a single hydrogen atom releases roughly 4 million times more
Where nuclear energy is used
Fission is the basis of every working nuclear power station on Earth, and of nuclear weapons
Fusion is what powers the Sun and all other stars. Fusion is also being developed as a future energy source on Earth, but no commercial fusion power station exists yet
Radioactive decay is used in medical tracers, smoke detectors, thickness gauging, and (on a planetary scale) to keep the Earth's interior hot enough to drive plate tectonics