bond length question

[OU11BB]

Which of the following has the shortest bond length?
C-F
C-Cl
C-Br
Si-F

and...

which of the following has the longest bond length
C-F
C-Cl
S-O
I-Br
C-I

there are no explanations for these. the answers are A and D respectively.
could somebody briefly explain this to me. Is this part of some periodical trend? thank you very much.

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[CANgnome]

my newbie but studied senses tell me:

that length depends on atomic radius. so carbon < Si and F < all halogens

so 1) = C-F = A

2) is one of the last 2.

atomic radii goes down as you go right and up through the periodic table.

but i would go with higher number of orbitals = greater length. Br > C

 

[Baylor2011]

Which of the following has the shortest bond length?
C-F
C-Cl
C-Br
Si-F

and...

which of the following has the longest bond length
C-F
C-Cl
S-O
I-Br
C-I

there are no explanations for these. the answers are A and D respectively.
could somebody briefly explain this to me. Is this part of some periodical trend? thank you very much.

1.) Flourine is the most electronegative element there is...therefore, shortest bond length since itll be "pulling" the carbons electrons toward it.

2.) Easy...two halides don't typically bond together because of 1.) the large atomic radii, and 2.) they're both pretty electronegative, thats why you typically see halides bonded to elements of lesser electronegativities.