Anegatively charged balloon has 2.6 µc of charge. how many excess electrons are on this balloon? the elemental charge is 1.6 × 10−19 c. answer in units of electrons.

The given 2.6 µC of charge is due to a buildup of electrons, each of which has a charge of 1.6 x 10^-19 C. The 2.6 µC is equivalent to 2.6 x 10^-6 C, so we can divide this by the individual charge of an electron:
2.6 x 10^-6 C / 1.6 x 10^-19 (C/electron) = 1.625 x 10^13 electrons