Both are used.
Uranium mainlyPlutonium and Uranium in fission weapons, Lithium deuteride in fusion weapons, occasionally small amounts of Tritium gas to boost fission weapons with fusion.
Nuclear bombs use nuclear fission of some heavy element, usually uranium or plutonium. Thermonuclear bombs use the detonation of a fission bomb to ignite the fusion of hydrogen. Such weapons are more powerful than ordinary nuclear weapons because nuclear fusion releases more energy than nuclear fission, and because the process of fusion itself can be used to ignite more fission.
Nothing but the terminology. "Atomic" was the term used in the early days of nuclear weapons and nuclear power. "Nuclear" (describing the fission process of nuclear power and nuclear weapons) became the term when fusion bombs became reality, as Atomic can refer to both fission and fusion processes.
Nuclear fission is used in nuclear weapons to create what some might call an atomic blast (nuclear blast). Nuclear fission used this way can also be applied in special complex designs to generate enough thermal energy (heat) to initiate a fusion reaction. This creates an even bigger nuclear blast.
Nuclear detonations can be classified into two main types: fission and fusion. Fission involves the splitting of atomic nuclei, while fusion combines atomic nuclei to release energy. Fission is typically used in nuclear power plants and atomic bombs, while fusion is used in more powerful thermonuclear weapons.
Nuclear weapons' yield is derived primarily from fission. Thermonuclear weapon's yield is derived mainly from fusion. Thermonuclear weapons are multistage weapons -- x-rays from a nuclear primary trigger are used to trigger ablation in the pusher of the secondary to compress it, which is responsible for the fusion reaction.
Nuclear weapons developed by the Manhattan project for the Allies were Fission weapons called Atomic bombs. Large scale Fusion weapons developed by Hungarian Edward Teller in USA after WW2 were called Hydrogen Bombs. However during 1942 the Nazis developed a hybrid fusion boosted fission weapon, in which hollow charge explosives were used to cause a plasma pinch, a kind of flash of neutrons to ignite a Fission explosion.
The radioactive elements plutonium or uranium are the elements that are used in nuclear weapons that create nuclear fission. Isotopes of hydrogen are used in nuclear weapons that create nuclear fusion.
nuclear fusion
Fission. Fusion has never been used on Earth, except for nuclear weapon tests.
Nuclear fusion and nuclear fission are two types of nuclear reactions that release energy. Fusion combines atomic nuclei to create heavier elements, while fission splits atomic nuclei into smaller fragments. Fusion powers the sun and hydrogen bombs, while fission is used in nuclear power plants and atomic bombs.
The two types of nuclear energy are nuclear fission nuclear fusion. In nuclear fission, the nuclei of the atoms are split. In nuclear fusion, as the name suggests, the nuclei of the atoms are joined together.