Californium is a radioactive transuranic element, and is 'man-made'. Although it is not naturally occurring on earth, it does seem to come about in other places in the universe (pretty cool, huh?). It is used in starting nuclear reactors and medical treatment of cancer.
Argon is a natural element found in the air.
Tin
Carbon, it is found in every human cell and as diamonds and graphite
Uranium, element number 92, is the largest naturally occurring element. However, francium, 87, and astatine, 85, along with any element with an atomic number larger than 92 are not found in nature. They are produced in the laboratory. If they do occur naturally they are in exceedingly small quantities. So to answer your question "How many elements can't be found in nature?" about 16 or a few more.
All elements in the Periodic Table contain only one type of atom.
Californium is a pure element.
Californium is an artificial chemical element.
Californium is an artificial chemical element !
Californium is an artificial element; the natural element exist only in infinitesimal traces in uranium ores.
Californium is a man made element; usually found in nuclear physics/radiochemistry laboratories.
Yes, californium is a pure chemical element, not a compound or mixture.
Californium is a chemical element !
Californium is an artificial element and is difficult to prepare and to separe this element.
Californium is an artificial element.
The element Californium is reactive.
Californium does not occur naturally. It is produced as a result of nuclear explosions and nuclear experiments.
It's a silvery metal, which is solid at room temperature.