A fluorine atom has seven valence electrons. ... Carbon will then have five valence electrons (its four and the one its sharing with fluorine). Covalently sharing two electrons is also known as a “single bond.” Carbon will have to form four single bonds with four different fluorine atoms to fill its octet.
60 elements! I don't exactly know every element known, so if you are asking that, please tell us, but what I do know is that there were 60 elements in the periodic table by 1860.
I'm pretty sure it's the same 2mm = 2cc = 2c^2
