The amount of the electron's charge:

Correct answer: b −1.60 × 10⁻¹⁹ coulomb

The electron's charge is −1.60 × 10⁻¹⁹ coulomb.

Why the other options are wrong

• a −9.110 × 10⁻²⁸ coulomb: 9.110 × 10⁻²⁸ is the electron's mass in grams, not its charge; the charge is −1.60 × 10⁻¹⁹ coulomb.
• c 9.110 × 10⁻²⁸ coulomb: This is the number for the electron's mass, and its charge must be negative; it is −1.60 × 10⁻¹⁹ coulomb.
• d 1.60 × 10⁻¹⁹ coulomb: The size is right but the sign is wrong: the electron's charge is negative, −1.60 × 10⁻¹⁹ coulomb.