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gsenviro eNotes educator| Certified Educator

Atoms have two very important constituents: a nucleus and an electron cloud. The nucleus is composed of protons and neutrons, while the electron cloud contains the negatively charged electrons. Atoms form elements and thus are all around us. We can also make new atoms, by one of the two processes: nuclear fusion and nuclear fission. Fusion is the reaction in which smaller nuclei come together to form larger nuclei. Fission, on the other hand, breaks down heavier nuclei into smaller nuclei. 

The process of nuclear fusion takes place in stars, where hydrogen is converted to helium and so on. This process can go on, depending on the mass of the star, until we get iron. During the last moments of the star, further fusion causes heavier elements to be formed, all the way up to uranium. Scientists have successfully created heavier elements (beyond uranium) by bombarding elements with other elements or particles and have achieved atoms of newer, heavier elements. The only downside is that these super-heavy nuclei are unstable and decay to smaller nuclei.

Nuclear fission can be used to break larger nuclei into smaller ones and thus we can create atoms of lighter elements. An example is the decay reaction of uranium which generates lead atoms.

The process of creating atoms is very difficult; in general scientists don't do this.

Hope this helps.