07 September, 2008

Why is mercury liquid?

The answer is clearly presented here. I find very interesting that mercury does not crystallizes at the room temperature not only due to the filled atomic shells (the Hg configuration is [Xe] 4f14 5d10 6s2), but also because of relativistic effects, which decrease the radius of the 6s orbital.

Mercury is a liquid at room temperature because the "relativistic contraction" of its atomic orbitals makes it behave chemically almost like a noble gas, not wanting to share electrons with other atoms, even other mercury atoms! Note that mercury is monatomic in the gas phase, just like a noble gas. Of course this should not be pushed too far; mercury is not a noble gas. There are enough outer-electron interactions for mercury to remain a liquid (radon, 22 amu heavier, is a gas), to conduct electricity, and to participate in ordinary chemical reactions...

No comments: