The mass of a nickel coin is 5 g. 1 mol of Ni weighs 58 g. 1 mol contains 6.022 x 10²³ atoms of Ni. therefore in 58 g there are 6.022 x 10²³ atoms of Ni then in 5 g the number of Ni atoms are - 6.022 x 10²³ /58 x 5 = 5.2 x 10²² Ni atoms Therefore number of Ni atoms are 5.2 x 10²² atoms in a nickel coin
