how is a sample of an n type semiconductor electrically neutral though it has excess of negative charge carriers?

Because in a sample of n-type semiconductor, the number of conduction electrons is high as compared to the number of holes but the semiconductor material is electrically neutral. And this is because of the charge of excess electrons that are just equal and opposite to the charge of ionized immobile cores of the lattice.
In a n-type semiconductor, there are more free negative carriers than postive carriers but the amount of total negative and positive carriers is the same