Is hydrogen a metallic element?
Date: Before 1993
Is hydrogen a metallic element? If not, why is it on the left
side of the periodic table?
Hydrogen is not a metallic element despite the placement on the
left side of the periodic chart. I think that most modern periodic tables
place it both on the upper left (its periodic position) and on the upper right
next to Helium (its position as a gas). The reason that it was put on the
upper left of the table originally is because the column IA is home to all
elements with 1 electron in the outermost s-orbital. Hydrogen certainly meets
this criteria, however it is physical properties are more consistent with the
gases grouped at the upper right.
Just to expand on Mike's answer a little. The most common phase
of hydrogen (that is, pure hydrogen) is hydrogen gas. Two hydrogens form a
chemical bond to form H2. H2 does have a lot of physical properties which are
similar to the upper-right gases. However, solid hydrogen can be formed at
cryogenic temperatures (REAL cold) and there is some limited evidence that it
may be metallic (i.e. conduct electrons like a metal does). There are some
decent theoretical reasons for this to happen too...but it is still an issue
of some dispute if I recall.
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Update: June 2012