Answer
The larger atom or ion is:
a. $K $
b. $F^- $
c. $Cl^-$
Work Step by Step
a. Cations are smaller than the atoms from which they are formed. So, $K $ is larger.
b. Anions are larger than the atoms from which they are formed. So, $F^-$ is larger.
c. Both $Ca^{2+}$ and $Cl^-$ are isoelectronic, but $Cl^-$ has fewer protons than $Ca^{2+}$. This results in less pull on the electrons and a larger radius of $Cl^-$ , for it has a smaller number of electrons.
