The azimuthal quantum number (l) determines its orbital angular momentum and describes the shape of the orbital.
s-orbitals (for example 1s, 2s) are spherically symmetric around the nucleus of the atom.
p-orbitals are dumb-bell shaped. l = 0,1...n-1, when l = 1, that is p subshell.
d-orbitals are butterfly shaped.
1 mole of platinum has a mass of 195 g therefore 1 atom will have a mass of 195 g /(6.02 ×10^23) = 3.239 × 10^-22 g
Density is given by dividing mass by volume, thus to get volume, mass is divided by density.
The volume = (3.239 × 10^-22)/21.4
= 1.514 × 10^-23 cm³
But volume of a sphere is given by 4/3πr³
Therefore, r³ = 3.6129 × 10^-24
r = ∛(3.6129 × 10^-24)
= 1.534 × 10^ -8 cm
Therefore, the radius of the platinum atom is 1.534 × 10^-8 cm