A neutral atom will have the same number of electrons as protons. Since you did not mention that it was ion, I will assume that it is a neutral atom.
In a neutral atom, the number of electrons is the same as the number of protons. An an ion, the number of electrons may be less than or even greater than the number of protons depending on the charge.
An atom is defined by the number of protons it has. If you change the number of protons, it becomes a different atom. However, if you change the number of electrons it has, it is the same atom but it is called an ion because it will have a different charge. If you change the number of neutrons, you do not change the atom, but you change the overall mass of the atom. Keep in mind that a neutron is as heavy as a proton, and that the mass of an electron is almost negligible when compared to the mass of a proton and neutron.
As this is a neutral atom, the number of electrons should be the same as the number of protons. There are 3 electrons in this atom. This would be the atom lithium.