Yes, an electron can be removed from an atom. This process is known as ionization. When an electron is removed from an atom, the resulting species is called an ion.
The mass of the atom would remain almost unchanged when an electron is removed. The mass of an electron is extremely small compared to the mass of the atomic nucleus, which is composed of protons and neutrons. The mass of an electron is approximately 1/1836 times the mass of a proton or neutron. Therefore, removing an electron has a negligible effect on the overall mass of the atom.
However, it is important to note that the ionized atom would have a different charge than the neutral atom. If an electron is removed, the resulting ion will have a positive charge equal to the number of protons in the nucleus minus one (assuming only one electron is removed). For example, if a neutral hydrogen atom (which has one proton and one electron) loses its electron, it becomes a hydrogen ion with a charge of +1.