CHEMISTRY COMMUNITY

I'm curious as to why barium has a greater ionization energy than cesium? I figured that the two valence electrons in barium, compared to the one in cesium, would provide a greater electron-electron repulsion; therefore making it easier to remove an electron from barium.

Ionization energy increases left to right of the periodic table. Barium comes after Cesium meaning it has one more electron. More electrons means the strength of electron shielding increases. Therefore, Barium has more electron shielding.

The electron shielding doesn't outweigh the increase in nuclear charge when moving left to right on the periodic table. Therefore, since the electrons are pulled stronger into the nucleus, it's harder to remove and electron so ionization energy is greater. The added electron shielding going from Cs to Ba is also limited since the added electron is added to the same subshell which means the shielding isn't too great, especially in comparison to the effect of the added proton when going Cs to Ba.

what does ionization energy mean?

I think it means the energy required to take one electron away from the atom.

Ionization energy is the energy required to take an electron away from an atom. In other words, a higher ionization energy signifies that it is harder to strip an electron away. It gets higher as you move from the bottom left to the top right of the periodic table because of higher proton counts and less energy levels. Elements with near max valence electrons tend to take electrons to make a full 8-valence electron.

Atomic radius...
- increases in atomic size down the periodic table, as shells increase
- decreases across the periodic table from left to right

Ionization energy (the energy needed to add to remove an electron)...
- decreases down the periodic table
- increases across the period table from left to right

Oxygen is to the right of Nitrogen, why does it have a lower ionization energy than Nitrogen if ionization energy increases to the right?

I believe oxygen has a lower ionization energy due to the fact that its 8th electron becomes paired (the up and down spin) versus filling a new orbital. There would be more electron repulsion in this pair versus the other 3p electrons that are in their own orbital (x,y,z)

Thank you!

Christine Chow 4G wrote:I believe oxygen has a lower ionization energy due to the fact that its 8th electron becomes paired (the up and down spin) versus filling a new orbital. There would be more electron repulsion in this pair versus the other 3p electrons that are in their own orbital (x,y,z)