The number of lead atoms that are in a cube of lead that has a volume of 2.12 cm³ if the density of lead is 11.3 g/cm³ is 6.959 x10^22 atoms
calculation
step 1:find the mass of lead = density x volume
= 2.12 cm³ x 11.3 g/cm³=23.96 grams
step 2: find the number of moles of lead
moles= mass/molar mass
23.96 g/207.2 g/mol= 0.1156 moles
step 3: use the Avogadro's law constant to find the number of atoms
that is 1 mole = 6.02 x10^23 atoms
0.1156mole = ? atoms
by cross multiplication
(0.1156 moles x 6.02 x10^23) ÷ 1 mole=6.959 x10 ^22 atoms