The two dimensions of aluminum foil are given 13.72 cm and 8.63 cm respectively with mass 3.1 g.
The density of aluminum is 
. It is defined as mass per unit volume thus, volume of aluminum can be calculated as follows:
Putting the values.
The volume of cuboid is 
, the length and breadth are given, height can be calculated as follows;
Putting the values,
Or, approximately 9.7\times 10^{-3}cm
Therefore, thickness of aluminum foil is 
The molecular formula of chlorofluorocarbon is CF₂Cl₂
Molecular mass of CF₂Cl₂ is 120.9 g/mol
Mass of Cl in 1 mol - 2 x 35.5 = 71 g/mol
in 120.9 g of compound - 71 g of Cl
Therefore in 38 g of sample - 71/120.9 x 38 g of Cl
Mass of Cl in 38 g - 22.31 g of Cl
This is the electron configuration of neptunium:
<span>Rn 5f4 6d1 7s2
</span>or, if you want to complicate:
<span>1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f4 6d1
</span>Since there are 93 electrons, they make up 5f4 altogether.
