The mass of an atom cannot be changed by any means, as it is a fundamental property of the atom itself. The mass of an atom is determined by the total mass of its protons, neutrons, and electrons.
Protons and neutrons, which reside in the nucleus of an atom, have a mass of approximately 1 atomic mass unit (u) each. Electrons, which orbit around the nucleus, have a significantly smaller mass compared to protons and neutrons. The mass of an electron is about 1/1836th of the mass of a proton.
The number of protons and neutrons in the nucleus determines the mass number of an atom, which is typically denoted as A. The atomic mass of an element listed on the periodic table represents the average mass of all the naturally occurring isotopes of that element, taking into account their relative abundances.
So, while the mass of an atom cannot be changed, it is possible to change the number of protons, neutrons, or electrons in an atom through various nuclear or chemical reactions. However, such changes to the atomic structure result in the formation of different elements or isotopes, rather than altering the mass of the original atom.