Question

use the periodic table to compare the sizes of ionic radii with the corresponding atomic radii or other ionic radii. choose from smaller and larger in the blanks below:
a sodium cation is than a sodium atom.
a phosphorus anion is than a phosphorus atom.
a magnesium ion is than a sodium ion.
a chlorine ion is than a phosphorus ion.
a potassium ion is than a sodium ion.
done
smaller
larger

Explanation:

1. Sodium cation ($\text{Na}^+$) loses an electron, reducing electron-electron repulsion and shrinking the electron cloud, so it is smaller than the neutral Na atom.
2. Phosphorus anion ($\text{P}^{3-}$) gains 3 electrons, increasing electron-electron repulsion and expanding the electron cloud, so it is larger than the neutral P atom.
3. $\text{Mg}^{2+}$ and $\text{Na}^+$ are isoelectronic; $\text{Mg}^{2+}$ has more protons, pulling electrons closer, so it is smaller than $\text{Na}^+$.
4. $\text{Cl}^-$ and $\text{P}^{3-}$ are isoelectronic; $\text{Cl}^-$ has more protons, pulling electrons closer, so it is smaller than $\text{P}^{3-}$.
5. $\text{K}^+$ has an additional electron shell compared to $\text{Na}^+$, so it is larger than $\text{Na}^+$.

Answer:

1. A sodium cation is smaller than a sodium atom.
2. A phosphorus anion is larger than a phosphorus atom.
3. A magnesium ion is smaller than a sodium ion.
4. A chlorine ion is smaller than a phosphorus ion.
5. A potassium ion is larger than a sodium ion.