Why Is Science So hard?

Science is "hard" because we know a lot about alot of things in science. If you are learning about isotopes in school, you are learning about things that no one anywhere had even thought of 150 years ago. Maybe 70 years ago, there were only a few hundred or a thousand people alive who knew very much about isotopes. All of science is like this, we build on what people learned (or thought they learned) before so, to work on the cutting edge of science, you have to learn what everyone else had learned and then learn new things that no one ever knew before. As far as isotopes, read your text book or do you own research on the web. To give you a hint, "normal" atoms of a particular element have a given number of protons (which is what defines the element) and some number of nuetrons. There may be some atoms of that particular element with an extra nuetron or two. These isotopes have the same basic properties (they are still that element) but their nuclear properties will be a little different. Hope this helps