Why The Atom is Neutral and the Nucleus is not

The Atom is electrically neutral, as a whole it has no charge.

At the centre  it contains a nucleus which is very very very tiny when compared to the whole size of the atom.

Unlike the atom the nucleus is not electrically neutral, but due to the its content the nucleus is positively charged.

The space between the atom borders (if it has borders) and its nucleus is filled with electrons which are moving around the nucleus.