Hard to say.
Many countries make nuclear weapons behind other countries backs. Some countries are not announcing when they complete testing or development for nuclear warheads, so the world may never know.
The atomic bomb was the first nuclear weapon ever made during World war two and it was the first weapon that have been tested before Hiroshima was under attack.
nuclear chemicals such as plutonium
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.
In recent months both Iran and North Korea have been identified as potential nuclear threats. North Korea has successfully tested several nuclear devices. Iran is still developing the technology.
* 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
Originally as a defense against Nazi Germany possibly making one.
Uranium 235, or plutonium, depending on weapon design
Yes they are. They are one of the World's most powerful weapon has ever made.
first new clear weapon made is 1996
nuclear energy was first invented for a weapon of mass destruction (WOMD) but it was later developed as a main ingredient in the narcotic known as Molly (MDMA)
A detailed answer to the question can be found in John Forge's book The Responsible Scientist.
The cobalt bomb is a theoretical type of nuclear weapon designed to produce massive amounts of radioactive cobalt-60. It has not been built or tested because of the extreme consequences it would have on the environment.