# Why are the lighter halogens gases?

In the periodic table of the elements, only a few of the elements are gases at standard temperature and pressure. Those elements include the noble gases some of the halogens, and a few of the elements next to them, i.e. oxygen and nitrogen.

So why are these elements gases?

-
You could just as well turn this around and ask why STP lies in a range where the elements and common compounds comes in all three "usual" states of matter. And then the answer takes on the aspect of the weak anthropic principle. – dmckee Feb 4 '11 at 0:30
Can't say I understand the downvote. The question has an objective answer at the border of physics and chemistry. – dmckee Feb 4 '11 at 1:27
The downvote is for the hint to that closed "Why are the alkali...." – Georg Feb 4 '11 at 1:39
Downvote revoked. – Georg Feb 4 '11 at 23:10

 Ever heard of Iodine, a solid? Or from Bromine, a liquid? -1 – Georg Feb 4 '11 at 1:14 But those aren't the light ones, are they? – Lagerbaer Feb 4 '11 at 3:12 Light halogens are the most electronegative elements in the periodic table en.wikipedia.org/wiki/Electronegativity so their bonds are among the strongest ones the elements may exhibit. That's why they instantly form the diatomic molecules, $F_2$ and $Cl_2$. After all, the same is true for nitrogen and oxygen next to fluor in the periodic table, too. The resulting diatomic molecules are symmetric and still "electronegative", i.e. "thirsty to steal e-", but in the fluor or chlor gas, there is no one who could donate electrons so the molecules don't grow and don't interact with each other. – Luboš Motl Feb 4 '11 at 7:03 Your Comments reads: "The halogens are ..." doesn't it? – Georg Feb 4 '11 at 10:31 Another two errors: the bonds in F2 and Cl2 are rather weak compared to bonds in O2, N2 and H2 ! ( that is why they are so reactive!)Next: ".. not strongly polarized..." Such symmetric molecules are not at all polarized! Boiling point is "caused" by dispersion forces only. @Lubos: Electronegativity gives some hint about polarization of bonds between different elements, there is almost no connection to the binding strength. – Georg Feb 4 '11 at 17:18