Chlorine, Cl2, is a gas at room temperature, but bromine, Br2, is a liquid. Why?
Chlorine would create a nonpolar covalent bond as each atom (with equal electronegativity) shared it's non paired electron. Nonpolar molecules have a very weak attraction to other nonpolar molecules, so a lower boiling point would result.
Wouldn't bromine do the same thing, since it also has one unpaired electron?
1 answer
Yes but the mass of a mole of Br2 is about 160 versus that of a mole of Cl2 of about 71. Big difference. Note the trend in group 17 (or VIIA depending upon the system you are using). F2 and Cl2 are gases. Br2 is a liquid. I2 is a solid.