Neon electrons

Beyond neon, electrons enter the third principal level. The 3s sublevel is filled at magnesium ... 

One trend worth noting involves the relative sizes of a set of isoelectronic ions—ions containing the same number of electrons. Consider the ions O2-, F, Na+, Mg2+, and Al3+. Each of these ions has the neon electron configuration. How do the sizes of these ions vary In general, there are two important facts to consider in predicting the relative sizes of ions the number of electrons and the number of protons. Since these ions are isoelectronic, the number of electrons is 10 in each case. Electron repulsions should therefore be about the same in all cases. However, the number of protons increases from... 

In this reaction, Na atoms lose one electron each to form Na+ ions, which contain only ten electrons, the same number as the preceding noble gas, neon. We say that sodium ions have the neon electronic structure Na+ is isoelectronic with Ne (Section 6-5). In contrast. Cl atoms gain one electron each to form Cl ions, which contain 18 electrons. This is the same number as the following noble gas, argon Cl is isoelectronic with Ar. These processes can be represented compactly as... 

Representative elements usually attain stable noble gas electron configurations when they share electrons. In the water molecule eight electrons are in the outer shell of the O atom, and it has the neon electron configuration two electrons are in the valence shell of each H atom, and each has the helium electron configuration. Likewise, the C and O of CO2 and the N of NH3 and the ion each have a share in eight electrons in their outer... 

The 3s and 3p orbitals are filled in going across the third period of the periodic table from sodium through argon. Atoms of these elements, like all atoms beyond neon, have their 10 innermost electrons in the neon electron configuration of ls 2s 2p. Therefore, these atoms have a neon core, which may be designated Ne ... 

Electron configurations of atoms were discussed in some detail in Chapter 3. Emphasis has been placed on the stability of a stable octet of outer shell electrons, which is characteristic of a noble gas. Such an octet is in the ns np electron configuration. The first element to have this configuration is neon, electron configuration WliP lp. (Recall that helium is also a noble gas, but with only 2 electrons, its electron configuration is simply b. ) The next noble gas beyond neon is argon, which has the electron configuration ls 2s 2p 3s 3p, commonly abbreviated NelBs Bp . 

With this notation, the electron configuration of element number 11, sodium may be shown as Ne 35, which is an abbreviation for 15 25 2/7 35. The former notation has some advantage in simplicity, while showing the outer electrons specifically. In the example just cited it is easy to see that sodium has 1 outer shell 35 electron, which it can lose to form the Na ion with its stable noble gas neon electron configuration. 

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