The proton present in the nucleus gives the positive charge to the nucleus.
Explanation:
In the nucleus, there are two particles present, one is proton and the other one is neutron. Neutron is neutral in charge or say, it has no charge. Proton has the positive charge.
Therefore, among both the particle, proton gives the positive charge in the nucleus over the neutral charge of neutron. Thereby, nucleus acquires the positive charge from the proton. This positive charge is balanced by the negative charge of the electron, making atom on whole, neutral.