When Someone Wants A Nuclear War , You Are Defended
The meaning of the word nuclear weapon, is a weapon that has a nuclear warhead on it.
The main advantage to having nuclear powered submarines is that a nuclear powered submarine can, if designed wisely, stay submerged for months on end. The only limitation really is food and the crew's psychological state. This is extremely useful in nuclear deterrance considering that a nation can send out nuclear powered, nuclear weapon equipped submarines on patrol for use in case of a nuclear exchange. If an attacking nation destroys the missiles silos of it's target and it's nuclear armed bomber wings, the defending nation would still have the use of it's nuclear weapons onboard it's ballistic missile submarines.
USA, Russia, UK, PRC, France, India, Pakistan, North Korea are known for having nuclear weapon. Israel probably also owns nuclear weapon but never officialy declared it.
There are two questions here. Why does Iran need a nuclear bomb? -- Iran does not NEED a nuclear bomb. Iran WANTS a nuclear bomb since having a nuclear weapon would, in Iran's view, lessen the advantage that Israel has over its neighboring Islamic States. It would also be a symbol of Iranian power and a projection of Iranian influence and civilization. When will Iran have a nuclear bomb? -- The timeline for Iran gaining a nuclear weapon is unclear. It is likely that Iran will have sufficient fissile material to make a bomb by late 2015 or early 2016. However, the Israeli Mossad has performed a number of operations aimed at delaying the creation of such a weapon.
This nuclear weapon is called an atomic bomb or a nuclear bomb
Nuclear weapon detonations
If by "bomb" you mean a conventional explosive weapon, then the nuclear weapon is more powerful.
To defend against someone else having them. Same as any other weapon.
nuclear chemicals such as plutonium
NO
no
No. LLNL even tested several Uranium-Hydride bombs in the 1950s. Even though their computer models said the devices should explode, none gave a nuclear yield. One could use the waste from the reactor as a Radiological Weapon, but the reactor itself is not useful as a weapon.