Which of the following elements has an ionic radius greater

than its atomic radius
a) Ca c) Fe
b) Li d) N

Which one GAINS electrons to become an ion? Gaining electrons, since they go into a shell already occupied by other electrons, causes the radius to be larger because of the repulsion forces between like charges.

So its nitrogen ?

That would be my answer.

To determine which element has an ionic radius greater than its atomic radius, we need to compare the atomic radius and the ionic radius for each element given.

First, let's understand what atomic radius and ionic radius mean:

- Atomic radius: It is the size of an atom, measured from the nucleus to the outermost electron shell.

- Ionic radius: It is the size of an ion, which is either an atom that has gained or lost electrons.

To compare the atomic radius and ionic radius, we need to know the trend in atomic and ionic sizes across the periodic table:

- Atomic size generally decreases from left to right across a period due to increasing nuclear charge pulling the electrons closer to the nucleus.

- Atomic size generally increases from top to bottom within a group due to the addition of new electron shells.

- Ionic radius of cations (positive ions) is smaller than the atomic radius because when an atom loses electrons, it removes electron-electron repulsion, causing the remaining electrons to be pulled closer to the nucleus.

- Ionic radius of anions (negative ions) is larger than the atomic radius because when an atom gains electrons, it increases electron-electron repulsion, causing the electrons to spread out.

Now, let's examine the given elements:

a) Ca (calcium): Calcium is in Group 2 of the periodic table. As it loses two electrons to form a Ca2+ ion, the ionic radius becomes smaller than the atomic radius. Therefore, Ca does not have an ionic radius greater than its atomic radius.

b) Li (lithium): Lithium is in Group 1 of the periodic table. When it loses one electron to form Li+ ion, the ionic radius becomes smaller than the atomic radius. Therefore, Li does not have an ionic radius greater than its atomic radius.

c) Fe (iron): Iron is in the middle of the periodic table, and it can form two common ions, Fe2+ and Fe3+. Both Fe2+ and Fe3+ ions have smaller ionic radii than the atomic radius of iron. Therefore, Fe does not have an ionic radius greater than its atomic radius.

d) N (nitrogen): Nitrogen is in Group 15 of the periodic table. When it gains three electrons to form N3- ion, the ionic radius becomes larger than the atomic radius. Therefore, N has an ionic radius greater than its atomic radius.

Therefore, the correct answer is d) N (nitrogen).