This nuclear weapon is called an atomic bomb or a nuclear bomb
Fukushima
The meaning of the word nuclear weapon, is a weapon that has a nuclear warhead on it.
something that is not good for the planet
The nuclear weapon called Little Boy.
An atomic fission machine (device) might be called a nuclear reactor or a nuclear weapon.
The largest KNOWN nuclear weapon was made by the Soviet Union (Russia) and was called the "Tsar Bomba" (King of Bombs). It had a yield of ~50MT.
An atomic weapon is an alternative name for a nuclear weapon, a weapon which derives its energy from the nuclear reactions of either fusion or fission.
Nuclear weapon detonations
If by "bomb" you mean a conventional explosive weapon, then the nuclear weapon is more powerful.
* Earthquake Richter 5.0 = 32 kilotons nuclear weapon, like was used at Nagasaki * Earthquake Richter 6.0 = 1 megaton nuclear weapon * Earthquake Richter 7.0 = 32 megaton nuclear weapon * Earthquake Richter 7.1 = 50 megaton nuclear weapon, Tsar Bomba, the largest nuclear weapon ever tested * Earthquake Richter 8.0 = 1 gigaton nuclear weapon, much larger than anything ever made
The first one used in combat was called Little Boy.