Analyze the properties of a sodium atom and a sodium ion. what are the differences in mass, stability, and reactivity that are caused due to the differences between the sodium atom and sodium ion?

The only real difference between Na and Na+ is the charge.  The only difference in mass is the single electron that is missing in the Na+ ion (this is negligible when the total mass of the atom is considered).  The missing electron also changes the electron configuration so that the valence shell of electrons (outer shell) has an octet (8 electrons).  This is the most stable electron configuration.  The sodium atom would be more reactive because it is in the less stable state and needs to lose an electron.