When electrons are removed from the outermost shell of a calcium atom, the atom becomes
an anion that has a larger radius than the atom.
an anion that has a smaller radius than the atom.
a cation that has a larger radius than the atom.
a cation that has a smaller radius than the atom.

When electrons are removed from the outermost shell of a calcium atom, the atom becomes A CATION THAT HAS A SMALLER RADIUS THAN THE ATOM.

The radius of an atom refers to the measure of how big the atom is. When an element loses electron, it becomes positive charge and is called cation. When an element gains an electron, it becomes negative charge and is called an anion. When an atom loses an electron, its size becomes smaller; when an atom gains an electron, its size becomes bigger. Thus, when electrons are removed from the outermost shell of calcium atom, the atom becomes smaller and is now known as a cation.