When an atom of a main group element forms a cation, how many electrons does it tend to lose?

1. A main group atom forming a cation strips off its whole valence shell. 2. Losing all the valence electrons leaves it with the electron arrangement of the noble gas before it. 3. That is why a group 2 metal such as calcium reliably gives a two plus ion rather than a one plus ion. 4. Core electrons lie too deep to be removed in ordinary chemistry, so they are never the ones lost. _Source: OpenStax Chemistry (CC BY 4.0), Ch 7 "Chemical Bonding and Molecular Geometry", section Electronic Structures of Cations_