What is the importance of mitosis cell division to unicellular organisms?

It is important because it maintains  the population of that organism through reproduction. this reproduction also helps to replace worn out or dead organisms.

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass

That is false even though water expands when frozen nothing changes at all