How do you arrange elements' ionic size?

Question

How do you arrange elements'  ionic size?

Jeremiah Adams · Accepted Answer

Well, compared to their parent atoms...........

An elemental anion is decidedly LARGER than its parent atom. And an elemental cation is decidedly SMALLER than its parent atom. Why so?

The ionic radii is listed in #"pm"=10^-12*m#; a measurement in #"Angstroms"#, #10^-10*m#, is more useful for a chemist...... Anyway, for the metallic cations, we see that the ionic radii, the orange circles, are greatly reduced with respect to the parent atom. Why? Because we are removing valence electrons, whose radius defines the atomic radius. And upon their removal these radii becomes decidely smaller......

On the other hand, the situation is reversed for anions with repsect to their parent atoms. Because the anions are reduced, another electron(s) have been added to the valence shell. This expands the anionic radii because the nuclear charge is still the same and the valence shell expands to accommodate the extra electron(s).......The ionic radius of the nitride ion, #1.71# #stackrel(@)A#, versus the atomic radius of #0.70# #stackrel(@)A#, for the nitrogen atom is quite persuasive of this argument.

Cooper Anderson · Answer

undefined Elements' ionic size is arranged based on their position in the periodic table. Generally, as you move from left to right across a period, the ionic size decreases due to increased nuclear charge and stronger attraction for electrons. Conversely, as you move down a group, the ionic size increases due to the addition of electron shells.

Owen Ambrose · Answer

undefined Ionic size, or ionic radius, refers to the size of ions formed by atoms when they gain or lose electrons to achieve a stable electron configuration.

To arrange elements' ionic sizes:

1. **Cation Size**: 
   - Cations are formed when atoms lose electrons. 
   - As you move across a period (from left to right) in the periodic table, cation size decreases. This is because atoms lose electrons to achieve a stable noble gas configuration, resulting in a decrease in electron shells.
   - As you move down a group (top to bottom) in the periodic table, cation size increases. This is because atoms add more electron shells as you move down the group.

2. **Anion Size**:
   - Anions are formed when atoms gain electrons.
   - Similar to cations, as you move across a period (from left to right) in the periodic table, anion size decreases. This is because although electrons are added, the effective nuclear charge increases, pulling the electrons closer.
   - As you move down a group (top to bottom) in the periodic table, anion size increases. This is because additional electron shells are added, leading to a larger atomic radius.

In summary, cation size decreases across a period and increases down a group, while anion size follows a similar trend.