What information does the period number give about an atom?​

All of the elements in a period have the same number of atomic orbitals. For example, every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons.Explanation:

It tells us the principle quantum shell in which the element lies in. In other words, it shows the total number of electron shells the atom has

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.