How does the size of oxygens nucleus affect the distribution

The protons which are present are positively charged that attracts and pulls the electrons closer to the water molecule. Thus, the water molecule's negative charge is distributed all over the atom of oxygen, producing a substantial negative charge.

Explanation:

The nucleus of the oxygen atom is made up of 8 neutrons and 8 protons. The protons which are present are positively charged that attracts and pulls the electrons closer to the water molecule.

Thus, the water molecule's negative charge is distributed all over the atom of oxygen, producing a substantial negative charge. While, as electrons have drifted away from water molecules, the atom of hydrogen are left with just a partially positive charge.