5.4+Nuclear+Energy

**Nuclear Fission**
In [|nuclear physics] and [|nuclear chemistry], **nuclear fission** is a [|nuclear reaction] in which the [|nucleus] of an atom splits into smaller parts (lighter [|nuclei] ), often producing free [|neutrons] and [|photons] (in the form of [|gamma rays] ), and releasing a tremendous amount of [|energy]. The two nuclei produced are most often of comparable size, typically with a mass ratio around 3:2 for common [|fissile] isotopes. [|[1]] [|[2]] Most fissions are binary fissions, but occasionally (2 to 4 times per 1000 events), three positively-charged fragments are produced in a ternary fission. The smallest of these ranges in size from a proton to an argon nucleus. Fission is usually an energetic [|nuclear reaction] induced by a neutron, although it is occasionally seen as a form of spontaneous [|radioactive decay], especially in very high-mass-number isotopes. The unpredictable composition of the products (which vary in a broad probabilistic and somewhat chaotic manner) distinguishes fission from purely quantum-tunnelling processes such as [|proton emission], [|alpha decay] and [|cluster decay] , which give the same products every time.

**Nuclear Fusion**

 * Nuclear fusion** is the process by which two or more [|atomic nuclei] join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of [|energy] . Fusion is the process that powers active [|stars], the [|hydrogen bomb] and experimental devices examining [|fusion power] for [|electrical generation].