Answer
(a) $2.0 \times 10^{10}$
(b) $8.6 \times 10^{-13}$
Work Step by Step
charge on one electron $e = -1.60 \times 10^{-19} C$
(a) Number of excess electrons $= \frac{-3.20 \times 10^{-9}}{-1.60 \times 10^{-19}} = 2.0 \times 10^{10}$
(b) One mole of lead contains $6.022 \times 10^{23}$ lead atoms
Number of atoms in the sphere $= \frac{8.00}{207.2}\times6.022\times10^{23}$
Excess electrons per lead atom $= \frac{2.0\times10^{10}}{\frac{8.00}{207.2}\times6.022\times10^{23}}=8.6\times10^{-13}$
