Problem with slipping chain
 

Ive recently been having a problem with my bikes chain slipping gears,or just coming off when I need it most (going through traffic). Now my question is this: is my chain too large for the sprockets or is it a problem with my rear derailer keeping the appropriate tension. Any advice will be highly helpful

One way to assess which gears it is (front or back) is ride slowly, braking and watch your front rings to see if the chain slips off.

It could be slipping because of:
1. worn gears/chain (your gears will wear out and look almost pointy while the spaces between the teeth will be shaped more like half ovals and not half circles like when it's new.)
2. If it only skips every 6-10 pedal strokes it could be a kinked chain (a link might be tight)..and this usual happens more in higher gears where the gear has a smaller diameter the chain cannot wrap around it properly. Simple bend the chain sideways back and forth to loosen it. Lube it all too.
3. maladjusted derailuer(s). A. If your rear, inside gears don't skip but your outer gear(s) do then you need to adjust the set screws.
3.B. If your bike is kind of new then the shifter cables are stretched out, causing the improper shifting.
4. you could have a bent tooth or derailuer hanger.

If it's not one of these then I'm stumped. Hope ya get 'er fixed!