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Name: Jon
Status: other
Age: 30s
Location: N/A
Country: N/A
Date: Around 1999 


Question:
I had a question about chemistry and am searching the internet for an answer.

I was wondering if you could be of any help. Knowing the properties of all of the atoms, can properties of molecules be calculated from this knowledge, or are molecular properties inheritant to the molecule itself.

For example: can the melting and boiling points for say methane or butane be calculated just knowing the all of the properties of C and H???


Replies:
Unfortunately, the individual properties of an atomic species do not reflect the properties of the molecule. The example of hydrogen and oxygen, forming water is perhaps a benchmark for your question.

Dr. Myron


Molecular properties are inherent to the molecule. They do depend on what atoms are in the molecule, but just knowing the properties of the free atoms doesn't tell you everything about the molecule.

The example you give, of melting and boiling points, actually confuses the issue. These are not molecular properties, but properties of a large collection of molecules. You can't know the melting and boiling points even if you know everything about the individual molecules. Those properties depend on how different molecules interact with each other.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois


The answer is that molecular properties are quite distint from atomic properties in general. The calculation you suggest would not work.

prof. topper


Properties of unknown compounds can be predicted somewhat (differing degrees of success, depending on complexity) just by their structure. But you need to know how the atoms are arranged, not just what atoms are there.

Donald Yee Ph.D.
San Francisco Estuary Institute
180 Richmond Field Station
1325 South 46th St. Richmond, CA 94804



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