The Electronegativity of Ions?

[Saberae]

Homework Statement

"Rank the following in the order of increasing absolute electronegativity: F, Li, Ti4+, P, H, C, Mg2+, Li+."

Homework Equations

The Attempt at a Solution

- I can rank neutral species no problem. Periodic table has that covered, and Pauling values are easy to find. Ions don't have this.

- I know these ions have an electron configuration of the noble gases: [He], [Ne], and [Ar] which are not electronegative, but due to the increases effective nuclear charge on the valence shell of these ions, I'm not sure if the same trend applies.

- I've looked into ionization energies, atomic radii, electron affinities, etc., but I'm really stumped. I can rank the ions on their own, and the neutral atoms on their own, but I'm not sure how to integrate them.

- As for the ions, I believe that it makes sense for Li+ to have the greatest EN of the three ions due to it being the harder specie. Harder species tend to have an increases EN, while softer ones have lower EN.

- My Inorganic textbook mentioned the following: "Li has a low electronegativity, the Li+ ion has a relatively high EN resulting from the extremely high second ionization potential." I looked up, and compared all the ionization energies pertaining to the valence electrons of each species, and the ranking came up as follows:

Li < P < H < C < Ti4+ < F < Mg2+ < Li+

I'm not sure how I feel about Mg2+ and Li+ being above F in electronegativity though, so I feel like I may be missing a factor. Please help!

 

[nate808]

Thank you for your post. Ranking the electronegativity of ions can be tricky, but you are on the right track with your approach. You are correct in considering the effective nuclear charge on the valence shell of the ions. This is an important factor in determining electronegativity.

In addition, it is important to consider the size of the ion. Smaller ions tend to have higher electronegativity because the valence electrons are closer to the nucleus and experience a stronger pull from the positive charge.

Based on this information, the ranking you have come up with is mostly correct. However, I would suggest swapping the positions of Mg2+ and Li+. While Mg2+ does have a higher effective nuclear charge, it is also larger than Li+, which lowers its electronegativity. Li+, on the other hand, is smaller and therefore has a higher electronegativity.

The correct ranking, from least to greatest electronegativity, is as follows:

Li < P < H < C < Ti4+ < F < Li+ < Mg2+

I hope this helps clarify any confusion. Keep up the good work in your studies!