Question

What is 5.05 x 10^-13? (5.05 times 10 to the power of negative 13?)

Answer 1

When working with scientific notation, you can just move the decimal place.  For positive powers, you would move the decimal place to the right, and for negative powers (like you have) you would move it to the left.  Take your number 5.05.  Since it is 10^-13, move your decimal point 13 times to the left.
Original number: 5.05
Moved to left once: 0.505
Moved to left twice: 0.0505
etc...
Moved to left thirteen times: 0.000000000000505 (your final answer)

Answer 2

$5.05*10^{-13}\to\boxed{0.505*10^{-12}}$

or you can write it like:

$5.05*10^{-13}=0.000.000.000.000.505$