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Name: Linda K. griffin's sixth grade science class
Status: N/A
Age: N/A
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Country: N/A
Date: 1999 

We would like to know why hydrogen has only a proton and no neutrons. Does the lack of a neutron influence hydrogen's volatile properties? Also, is the lack of a neutron the reason that hydrogen is not grouped with the noble gases?

Excellent question... Actually there are three types of hydrogen atoms. The most common type is "normal" hydrogen and only has 1 proton and 1 electron. A less abundant type, called deuterium contains 1 proton, 1 electron, and 1 neutron. A deuterium atom weighs twice as much as a "normal " hydrogen atom. There is also an even less abundant type of hydrogen atom, called tritium which contains 1 proton, 1 electron, and 2 neutrons. Tritium weighs three times as much as a "normal" hydrogen atom. For most purposes, all three of these types of atoms behave identically from a chemical perspective. However, from a nuclear perspective, they behave differently since they have different numbers of neutrons. Hydrogen is not in the noble gas family because its s orbital in its outermost shell (The first shell) is not filled. Members of the noble gas family have filled s and p orbitals in their outermost electron shell.

Hope this helps!

Dr. Brown from Tallahassee...

Well, helium has only filled s orbitals but it's usually the first two is said to have a "restricted valence;" only the s orbitals are considered to be part of the valence shell. Thus the hydrogen atom has it s valence half-filled and He has its valence completely filled, which is characteristic of rare-gas elements; low electron affinity, high ionization energy. In the second row, s and p orbitals are close enough in energy so that they now constitute the valence shell; thus when beryllium's 2s orbital is filled it still hasn't completed it's valence shell (although the filled 2s orbital is pretty stable and is sort of a pseudo-rare gas configuration.... Just putting in my 2 cents' worth.

-dr topper

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