Why eight electrons

It is clearly seen how strong the core-electron bond near the core is and that it neglect the electron-electron repulsion - The core with all positive charge is "located" in space 23, - , times smaller that whole electron cloud.

That means that the orbitals in question are: 1s, 2s, 2p, 3s and 3p. For each possible occupation of these orbitals by up to 18 electrons, energy levels can be obtained for the system as a whole.

It's important to remember that only discrete energy levels exist. It does not describe a switchlike situation - "is it stabilized or not", it only says that some are more stable that others. Real answer is - for many organic chemistry-relevant atoms, a shell with 8 electrons is by far the one with low energy state if one performs the quantum mechanical calculations.

Please excuse my rather layman reply, my specialism is not in chemistry or physics, but I felt this question is asking more why than how.

I suspect this more has to do with the fact that force is equalised. Even numbers. An odd number would suggest an unpaired electron which would suggest an unstable state. Think of it like having two cars pushing against each other evenly, or two equally attracted magnets. I don't think anyone knows why it's specifically 8, as opposed to 6 or 4 or 2.

It means they are in a low energy state. A high energy state is where an atom holds a potential to react. Take for example sodium - when introduced to water it reacts violently and explodes.

That is because, in simplistic terms, it transfers electrons between sodium and water. When an atom achieves 8 electrons, there's no more electrons for it to gain or lose IE if it was less than 8 it would have to gain additional electrons from some other material, and more than 8, it could lose some - essentially a reaction would occur.

So when we say stabilisation has occurred, we are essentially saying that conventionally the atom won't react. It has become stable. Edit: Not sure why the downvotes. No feedback, no correction. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Asked 5 years, 4 months ago. Active 2 years, 11 months ago. Viewed 23k times. Improve this question.

Community Bot 1. MartianCactus MartianCactus 4 4 gold badges 13 13 silver badges 19 19 bronze badges. There are far too many hidden sins in the phrasing that you quote "8 electrons", "stabilise" and a great deal of elaboration on those points is needed. Perhaps someone will be up to the task. You are looking for what we, in philosophy, call a "justification" for an idea.

It is clear you have already refuted the justification of "we've done this experiment millions of times, and here's what we've seen," so you are asking for an even better justification than that. There are also a variety of molecules in which there are too few electrons to provide an octet for every atom. Boron and aluminum, from Group III or 13 , display different bonding behavior than previously discussed.

These atoms each have three valence electrons, so we would predict that these atoms want to bond covalently in order to gain 5 electrons through sharing to fulfill the octet rule. However, compounds in which boron or aluminum atoms form five bonds are never observed, so we must conclude that simple predictions based on the octet rule are not reliable for Group III.

Consider boron trifluoride BF 3. The bonding is relatively simple to model with a Lewis structure if we allow each valence level electron in the boron atom to be shared in a covalent bond with each fluorine atom. In this compound, the boron atom only has six valence shell electrons, but the octet rule is satisfied by the fluorine atoms.

Lewis structure of boron trifluoride : Each pair of dots represents a pair of electrons. When placed between two atoms, the electrons are in a bond. A bond can be drawn as a line between two atoms, which also indicates two electrons. We might conclude from this one example that boron atoms obey a sextet rule. However, boron will form a stable ion with hydrogen, BH 4 — , in which the boron atom does have a complete octet.

In addition, BF 3 will react with ammonia NH 3 , to form a stable compound, NH 3 BF 3 , for which a Lewis structure can be drawn that shows boron with a complete octet. Boron trifluoride-ammonia complex : This covalent compound NH 3 BF 3 shows that boron can have an octet of electrons in its valence level.

Compounds of aluminum follow similar trends. Aluminum trichloride AlCl 3 , aluminum hydride AlH 3 , and aluminum hydroxide Al OH 3 indicate a valence of three for aluminum, with six valence electrons in the bonded molecule. However, the stability of aluminum hydride ions AlH 4 — indicates that Al can also support an octet of valence shell electrons. Although the octet rule can still be of some utility in understanding the chemistry of boron and aluminum, the compounds of these elements are harder to predict than for other elements.

Some elements, most notably nitrogen, can form compounds that do not obey the octet rule. One class of such compounds are those that have an odd number of electrons. As the octet rule requires eight electrons around each atom, a molecule with an odd number of electrons must disobey the octet rule.

Recall that the Lewis structure of a molecule must depict the total number of valence electrons from all the atoms which are bonded together. A stable arrangement is attended when the atom is surrounded by eight electrons. This octet can be made up by own electrons and some electrons which are shared. Thus, an atom continues to form bonds until an octet of electrons is made. The noble gases rarely form compounds. They have the most stable configuration full octet, no charge , so they have no reason to react and change their configuration.

All other elements attempt to gain, lose, or share electrons to achieve a noble gas configuration. The formula for table salt is NaCl. If sodium metal and chlorine gas mix under the right conditions, they will form salt. The sodium loses an electron, and the chlorine gains that electron. Sulfur, phosphorus, silicon, and chlorine are common examples of elements that form an expanded octet.

Phosphorus pentachloride PCl 5 and sulfur hexafluoride SF 6 are examples of molecules that deviate from the octet rule by having more than 8 electrons around the central atom. Show Sources Boundless vets and curates high-quality, openly licensed content from around the Internet. Licenses and Attributions. CC licensed content, Shared previously.