Answer:
We know when the no of protons (+ charge) is greater than the no of electrons (- charge), the nucleus pulls the electrons with greater force, hence making the size smaller. Clearly, the cations are smaller than the atoms, this largest atom/ion will be Ca.
K has 19 protons, 19 electrons
K+ has 19 protons, 18 electrons
Ca has 20 protons, 20 electrons
Ca2+ has 20 protons, 18 electrons
Li has 3 protons, 3 electrons
Clearly, the cations are smaller than the atoms, this largest atom/ion will be Ca.
Explanation: