Question

The number of free electrons in $1c.c.$ of Copper is

• A. $8.4\times {10}^{22}$
• B. $5.8\times {10}^{22}$
• C. ${10}^{15}$
• D. ${10}^{20}$

Answer 1

The correct option is A $8.4\times {10}^{22}$

Density of copper $\rho =8.89$ $g/c{m}^3$

Atomic mass of copper $M=63.54$ $g/mol$

Number of copper atoms in $1c{m}^3$ $N_{Cu}=\frac{\rho N_A}{M}=\frac{8.89\times 6.023\times {10}^{23}}{63.54}=8.4\times {10}^{22}$ atoms per $c{m}^3$

As one Copper atoms contributes one free electron.

Thus number of free electrons $N_e=N_{Cu}=8.4\times {10}^{22}$ electrons per $c{m}^3$