You may mean Ununoctium, created in Moscow in 2002. The proposed true name is Moscowium.
Plutonium, an element not found in nature, is formed from uranium during reactor operation
I think you may mean nuclear transmutation when an element irradiated in a reactor may be changed to another element. Uranium 238 changes to Plutonium 239 for example, but you don't say which substance you have in mind
Uranium and plutonium are naturally occurring elements found in the Earth's crust. They are formed through processes like nuclear decay of other radioactive elements or through supernova explosions. Both uranium and plutonium are used as fuel in nuclear reactors and in the production of nuclear weapons.
Tritium is formed by the capture of neutrons by deuterium (heavy hydrogen) which is in the heavy water in the moderator and coolant.
A non element. Steel is formed from Iron and carbon.
Hydrogen. It is also the lightest element and the first element that ever formed.
these "formed elements" are called the organelles.
Carbon
uranium
Carbon
An artificial boundary is a boundary that is man made instead of naturally formed by nature. These boundaries include fences and dams.
Plastic is artificial because it is not (formed as) a natural substance, not in or by living organisms, like animals, plants or microbes.