Chemistry Dictionary

Where can I find a good chemistry dictionary thats fast and would have easy things like molecule to hard things like Aufbau Principle and Hund's Rule?
A.
None of the online chemistry dictionaries I found are comprehensive enough to include those terms you mentioned. For the easier terms (such as your first two) I found very good definitions on Encyclopedia Britannica Online at:
      http://www.britannica.com/
For Hund's Rule, I  had to use the Google search engine:
     http://www.google.com
The best place to learn chemistry terminology is from a good General Chemistry textbook. There you will find those terms used in the proper context. For example, the chapter (or unit) on atomic structure will tell you all about the Aufbau Principle and Hund's Rule in the section about Electron Configurations. Also you will be given exercises and problems that use those terms. That will help you understand them. A dictionary is of very limited value in studying chemistry.

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