How does electron configuration effect electronegativity?

Question

Olivia Anton · Accepted Answer

Electron Configuration allows us to almost totally understand electronegativity!

The fundamentals of electron configuration, such as the fact that the n=1 electron shell contains only two electrons and is relatively close to the nucleus, should be known to anyone knowledgeable enough to ask this question. Let's look at the n=2 electron shell. That shell covers the elements from lithium to neon. When you open a new electron shell, you actually only do it once and it opens a whole bunch of possible places for electrons to hang out. so with lithium, you have 2 electrons in the n=1 shell (#1s^2#) and one electron in the n=2 shell (#2s^1#). Good? Well, now think about what is retaining that electron in place: the attraction to the positive charge of the three protons in the lithium nucleus. But, the two electrons in the n=1 shell also repel the single 2s electron, preventing it from sensing the attraction of all three protons. In fact, since the two n=1 electrons are nearer the nucleus than the 2s electron, it only perceives the attraction of one proton! The term "effective atomic charge" refers to this idea. For example, in lithium, the 2s electron experiences an effective atomic charge of +1. Adding another electron to the n=2 shell in beryllium results in an electron that is neither closer nor farther from the nucleus than the first n=2 electron, so it does not obstruct the nucleus's attraction. Each of the n=2 electrons experiences an attraction of +2, meaning that both are held more firmly in beryllium than the single electron in lithium. The effective atomic charge of beryllium for the n=2 electrons is +2. Using the same logic, fluorine has an effective atomic charge of +7 for n=2 electrons. Electrons have a strong attraction to be in the n=2 shell of fluorine. Let's now examine fluorine. However, there is still more room for an electron because the n=2 shell actually has eight slots for electrons. This additional electron will be attracted to the fluorine nucleus in the same way as the first seven n=2 electrons because it will be neither closer nor farther from the nucleus than the other seven. This is the source of electronegativity: if there is an available space in the outermost shell of an atom, electrons will gravitate toward atoms with large effective atomic charges. Since the attraction between the effective atomic charge and the electrons weakens with distance, each electron shell is farther from the nucleus than the one before it. For instance, oxygen, with an effective atomic charge of 6, and chlorine, with an effective atomic charge of 7, almost have the same attraction for electrons because the chlorine n=3 shell is farther away than the oxygen n=2 shell.

Cooper Adams · Answer

undefined Elegativity is influenced by electron configuration; elements with closer valence electrons and higher effective nuclear charge have higher electronegativity.