Given:
atomic mass of calcium is 40u.
No. of moles =given weight/molecular weight
No. of Cu moles=0.4/40=1/00=0.01moles
We know that 1 mole of any substance contains 6.023 x 10²³ atoms/ molecules/ions
1mole of Cu contains=6.023 x 10²³ atoms of Cu
0.01 mole of Cu contains =6.023 x10²¹ atoms of calcium.
∴The no. of calcium atoms in 0.4 u of calcium are 6.023 x10²¹ atoms
