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Octet Rule

What is the Octet rule?

In the field of chemistry there are many rules that apply to atoms, molecules and elements. One of them is the octet rule, which is based on the stability that a certain element can have, which in this case is a valence shell containing 8 electrons. This rule basically explains to us the way in which all the chemical elements can come to be combined.

Octet rule What is it, statement, characteristics, applications, examples

The octet rule says that atoms have more persistence when they have eight electrons and in this way, they achieve maximum stability since, when two equal atoms bond, they organize better.

This Article Also Includes:

  • Statement
  • Byte rule features
  • Who proposed it
  • History
  • Exceptions
  • Which elements do not meet the octet rule
  • Applications
  • Examples

Let’s Drive Right In;

Statement

The statement of the octet rule tells us that the elements always pursue an electronic configuration that is stable through the accumulation of eight elements which are located in the last orbits that are around the nucleus.

It is a rule that establishes that, only by means of the accumulation of eight electrons can it be achieved that the different molecules have a good stability , one that resembles those of noble gases.

The rule also states that atoms have a certain tendency to gain or lose electrons in search of the configuration that allows them to have the eight electrons and it tends to occur more frequently in the elements that are closer to the noble gases.

Byte rule features

Among its main features are the following:

  • It states that the atoms of two elements intertwine to try to complete the valence shell.
  • To achieve maximum stability, elements must gain or lose electrons when chemical bonds occur.
  • It can be applied to the way atoms form their bonds.
  • The bonds always depend on the nature that they have, as well as on the chemical properties of the molecules that result from the union.
  • The rule has the ability to predict the way many substances behave.
  • They can be represented by the Lewis Formula or by the Lewis Diagram.
  • The electronic octet of the rule can be reached by means of ionic , covalent , metallic and intermolecular bonds.

Who proposed the Octet Rule?

The octet rule was proposed in 1917 by Gilbert Newton Lewis , who noted that when atoms were combined with each other, they were looking at the same time for a way to achieve the same structural configuration that noble gases possess.

History

The history of the Rule of the Octet comes from the nineteenth century , a time when it was already known that molecular compounds were formed by combining atoms or molecules, making the valences stay tight.

It was Alfred Werner who succeeded in showing that the number of atoms found in groups with a central atom was usually 4 or 6, and those with 8 were rare.

Later, Richard Abegg in 1904 expanded the concept of the coordination number and began to give more importance to valence in order to identify the atoms that functioned as electron receptors.

Later, Lewis was in charge of establishing the rule of the octet or rule of eight and with it he created a division between the valence and the electrons .

Exceptions of Octet Rule

Not all elements and compounds that exist adhere to the octet rule, some of these exceptions are the following:

  • An atom or ion that has a valence electron that is not paired , which is known as a free radical. They are very unstable and dimerize spontaneously. Among them can be mentioned lithium , helium and hydrogen .
  • The aromatic compounds have pi delocalization electrons, which follow a different rule.
  • The aluminum has six electrons instead of eight.
  • The Beryllium also follow the rule because stabilization are only four electrons.
  • The boron because it forms substances with three single bonds.

Which elements do not meet the octet rule

There are some elements that do not adhere to the octet rule, among them we mention:

  • Hydrogens that have a single orbital in the valence shell and for this reason can only accept two electrons.
  • Boron that needs six electrons to be able to adhere to the rule, however it does not contain them.
  • Aluminum that can achieve maximum stability with only six electrons.
  • The beryllium that completes its last valence shell with only four electrons.

Applications

The octet rule can be applied mainly in the elements that are in the second period of the Periodic Table of the Elements. These only have 2s 2p sublevels which can have eight electrons in total. Every time one of these elements forms a type of covalent bond, then it acquires the electronic configuration equal to that of a noble gas.

Examples of Octet Rule

Two examples that can explain the chemical bond that occurs in atoms following the octet rule are the following:

Sodium Chloride (NaCl)

This type of compound has an ionic bond that occurs between the electronegative ions of sodium and chloride. The chlorine is 7 atom in their valence electrons and has the ability to achieve the configuration byte when gains an electron.

The sodium part has a shell that is more externally, it only has one electron, if it is lost, the shell that follows becomes the valence shell, which already has 8 electrons.

The cation in sodium and the anion in chloride then form an ionic bond and the resulting molecule has octet configurations on the two atoms.

Magnesium Oxide (MgO)

The bond between oxygen and magnesium is ionic in nature . The magnesium atom can lose two electrons very easily and thus achieves a stable electronic configuration when it binds to neon to form Mg2. Oxygen, for its part, gains two electrons to form O2. These two atoms have stable configurations that contain octets.

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