what is coulomb law without air medium
force of attraction or repulsion between two point charges, q1 and q2 at rest placed in "free space" separated by a distance r, is directly proportional to product of the charges and is inversely proportional to the square of distance between them i.e.
Here is a constant, its value is 9 x 109 N-m2/C2
eo is called permittivity of free space and is equal to 8.85 x 10-12 C2/N-m2.
Hope this helps.