Is it that the 4s is at times further from the nucleus?

Once p27 is excluded from the nucleus it cannot inhibit the cell's growth.

The city grew from several nuclei, the abbeys and a commercial centre.

That's what they used to say in 1910, when mad scientists thought you might get energy from the nucleus of an atom.

Then , where is the mean square distance of the electrons from the nucleus.

The model says that the electrons orbit only at certain distances from the nucleus, depending on their energy.

This is a measure of the distance out to which the electron cloud extends from the nucleus.

In other words, no matter what energy state an electron is in, it's possible for it to be any distance from the nucleus.

Break them down to their atomic substructure then rebuild from the nucleus up.

In these conditions, electrons become detached from atomic nuclei and move around at great speed.