A sample of pure gold has a mass of 10.2 g. Calculate the number of moles in the sample and gold atoms in the sample.

Explanation:

molecular weight of gold = 197

converting 10.2 g into moles

no of moles = 10.2 / 197

= .0518 moles

one  mole of any element contains 6.02 x 10²³ number of atoms

.0518 moles will contain 6.02 x .0518 x 10²³ atoms of gold

= .311 x 10²³ no of atoms of gold .

= 3.11 x 10²² no of atoms of gold

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8