[jcais]

Why is a C-Cl bond longer than a C-F bond? Is it because Cl has more protons, therefore there is a larger space around the Cl atom that does not provide room for C to be near it?

Wouldn't the C-Cl bond be shorter because Cl has more protons than F, so the Cl atom would pull the C atom closer to it because the more protons provide for more attraction to C's electrons?

Thank you!

[Mitch]

Protons are so small, on the scale of a femptometers; while atoms are on the scale of nanometers. The difference in volume of having 8 additional protons in chlorine is not the right track for this question.

[zephyrblows]

Mmm, jcais, your second consideration is true, but there are other factors that greatly affect the bond lengths.

In addition to other atoms, protons also attracts something MORE DIRECTLY...
HOWEVER, that something ITSELF have YET more decisive influence on your problem...   

[Ψ×Ψ]

What do you know about the relative sizes of the atoms?

[english]

Periodic trends are the decisive factor here...not how many protons one has over another.  This characteristic is offset by these trends.