Envision that you have virtually finished a an excellent meal, yet cannot put one more bite in your mouth due to the fact that there is no ar for it come go. The noble gases have actually the exact same problem—there is no room because that any an ext electrons in their outer shells. Castle are fully full and cannot handle any more.

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## Noble Gas Configuration

Sodium, facet number 11, is the very first element in the third duration of the regular table. The electron configuration is $$1s^2 2s^2 2p^6 3s^1$$. The very first ten electron of the sodium atom room the inner-shell electrons and the configuration of just those ten electrons is specifically the exact same as the construction of the element neon $$\left( Z=10 \right)$$. This offers the basis for a shorthand notation because that electron configurations called the noble gas configuration. The elements that are discovered in the last column of the periodic table are an important group of facets called the noble gases. They room helium, neon, argon, krypton, xenon, and radon. A noble gas configuration of an atom is composed of the element symbol of the critical noble gas before that atom, followed by the configuration of the continuing to be electrons. So for sodium, we make the substitution of $$\left< \ceNe \right>$$ for the $$1s^2 2s^2 2p^6$$ component of the configuration. Sodium"s noble gas configuration becomes $$\left< \ceNe \right> 3s^1$$. Table $$\PageIndex1$$ reflects the noble gas construction of the third period elements.

Table $$\PageIndex1$$: Electron configurations of Third-Period aspects Element NameSymbolAtomic NumberNoble Gas Electron Configuration
Sodium $$\ceNa$$ 11 $$\left< \ceNe \right> 3s^1$$
Magnesium $$\ceMg$$ 12 $$\left< \ceNe \right> 3s^2$$
Aluminum $$\ceAl$$ 13 $$\left< \ceNe \right> 3s^2 3p^1$$
Silicon $$\ceSi$$ 14 $$\left< \ceNe \right> 3s^2 3p^2$$
Phosphorus $$\ceP$$ 15 $$\left< \ceNe \right> 3s^2 3p^3$$
Sulfur $$\ceS$$ 16 $$\left< \ceNe \right> 3s^2 3p^4$$
Chlorine $$\ceCl$$ 17 $$\left< \ceNe \right> 3s^2 3p^5$$
Argon $$\ceAr$$ 18 $$\left< \ceNe \right> 3s^2 3p^6$$

Again, the variety of valence electrons rises from one come eight throughout the third period.

The fourth and also subsequent durations follow the same pattern, except for the usage ofa various noble gas. Potassium has actually nineteen electrons, one an ext than the noble gas argon, for this reason its configuration could be written as $$\left< \ceAr \right> 4s^1$$. In a similar fashion, strontium has two much more electrons 보다 the noble gas krypton, i beg your pardon would allow us to write its electron configuration together $$\left< \ceKr \right> 5s^2$$. All aspects can be represented in this fashion.