The excess electrons on the lead sphere can be calculated using the formula:
q = n × e
where q is the charge, n is the number of excess electrons, and e is the elementary charge.
The mass of the lead sphere can be converted to its amount of substance (in moles) using its molar mass, which is 207.2 g/mol.
n = mass / molar mass
n = 7.60 g / 207.2 g/mol
n = 0.0367 mol
The number of excess electrons can be calculated by rearranging the formula for q:
n = q / e
n = -3.90 × 10^-9 C / -1.60 × 10^-19 C
n = 2.44 × 10^10
Therefore, the excess electrons on the lead sphere is 2.44 × 10^10.