Question

Assume that each of copper atom has one free electron. estimate the number of free columns in 1 mg of copper

Answer 1

First of all we should find out number of atoms in 1mg of copper

Number of copper = number of moles × Avogadro's constant
= {given weight/atomic weight} × 6.023 × 10²³

Here, given weight = 10⁻³ g
atomic weight = 63.5 g/mol

So, number of atoms = (10⁻³/63.5) × 6.023 × 10²³
= 6.023 × 10²⁰/63.5

now, A/C to question,
In one atom of copper , one free electron
∴ 6.023 × 10²⁰/63.5 atoms of copper have 6.023 × 10²⁰/63.5 free electrons
e.g., 9.48 × 10¹⁸ free electrons

Answer 2

As we know quantisation of charge

i.e Q=±Ne

where Q is charge possessed by body

N is no. of electrons

e is charge of electron i.e 1.6*10 raise to -19 C

so we know no. of electrons i.e 9.48*10²⁸

by substituting we get

=±9.48*10²⁸*1.6*10-¹⁹

=1.517 C