Trends are bad, lack of trends is worse.

In Chemistry there are dozens of trends on the periodic table that we need to memorize. Atoms are bigger to the left and down. Atoms are more electronegative to the right and up. Atoms are more likely to lose electrons if they're to the left and more likely to gain electrons if they're to the right. But, as much as I hate memorizing trends, I have discovered something even worse.

As a general rule if an atom forms molecules it has a higher boiling point if it is bigger which is lower on the table but if it forms bonds between atoms then it has a higher boiling point if it is higher up on the table. I always thought molecules WERE bonds between atoms. Apparently not.

Example: In group 14, Carbon has the highest boiling point, Tin has the lowest. In group 17 (Halogens), Iodine has the highest boiling point and Fluorine has the lowest. Group 18 (Nobles Gases) have the same rule as group 17.

The only reason I really care is that I got a 99% on my chemistry test because I said Helium had the highest boiling point of the noble gases instead of Xenon. Annoying.