The octet rule is a simple chemical rule of thumb octet rule says atoms with 8 electrons in their outer shell are stable atoms tend to combine in such a way that they each have eight electrons in their valence shells, giving them the same electron configuration as a noble gas. Information and translations of octet rule in the most comprehensive dictionary definitions resource on the web. It continues to serve as a very useful guiding principle and can be a good starting point for more sophisticated theories. The octet rule states that atoms gain or lose electrons to attain an outer shell electron configuration nearest that of a noble gas. Atoms follow the octet rule because they always seek the most stable electron configuration. These patterns can be used to predict how elements will combine to form. So in this onehowto article were going to explain what is the octet rule in chemistry. What are some examples of how the octet rule is used. May 01, 2004 i just used the octet rules dating game in my chemistry class last week. The octet rule is a general rule of thumb that applies to most atoms. Octet rule simple english wikipedia, the free encyclopedia.
Exceptions to the octet rule h 3po 4 phosphoric acid under no circumstances can the second row elements be surrounded by more than eight electrons. Lewis dot diagrams show when valence electrons follow the octet or duet rule. Find materials for this course in the pages linked along the left. The octet rule may not also apply to certain elements, like phosphorous and sulfur, both of which can have 12 bonded electrons when bonded to 6 other atoms sf6 is an example, and boron, which can show up in configurations with less than 8 valence electrons like bf3.
First of all to state what the octet rule is again, it is a general rule of thumb that the main group elements the ones excluding the transition metals combine such that they have 8 valence electrons except for h and he, which need 2. The octet rule successfully explained the formation of chemical bonds depending upon the nature of the element. The duet rule applies to atoms closest to helium, which only has two valence electrons. When you add up all of the valence electrons for the molecule, you get an odd number. Nov 26, 2018 octet rule a rule stating that atoms lose, gain, or share electrons in order to have a full valence shell of 8 electrons. In an ordinary atom, the number of electrons equals the number of protons. All elements will perform whatever chemical processes are necessary so that they have the same number of valence electrons. The chemical elements with atomic numbers close to those of. The molecules of the halogens, oxygen, nitrogen, and carbon are known to obey the octet rule. Octet, in chemistry, the eightelectron arrangement in the outer electron shell of the noblegas atoms. The octet rule might be a general rule of thumb that may apply to most atoms. Oct 23, 2015 an easy way to understand the octet rule. However, there are a few stable molecules which contain an odd number of electrons. We present a generator of virtual molecules that selects valid chem istry on the basis of the octet rule.
Lewis structure, also called electrondot structure, is a structural formula in which electrons are represented by dots. The octet rule and periodic trends the cavalcade o. The octet rule in chemistry is the principle that bonded atoms share their eight outer electrons. The terms full octet and full valence electron count are not interchangeable although they are often used this way, as eight is not the preferred valence. Noble gases are very stable as their outermost shell is completely full, it has 8 electrons that are paired. In simple terms, molecules are more stable when the outer shells of their constituent atoms are empty, full, or have a multiple of 8 electrons in the outer shell. Contributions of lewis are expressed by his celebrated octet rule, which states that electron transfer or electron sharing proceeds until an atom has acquired an octet of electrons i. According to the bohr model, an atom consists of a nucleus of protons and neutrons orbited by. The octet rule states that atoms with an atomic number below 20 tend to combine so that they each have eight electrons in their valence shells, which gives them the same electronic configuration as a noble gas. It covers valence electrons, lewis diagrams, the octet rule, and more.
The octet rule is only applicable to the main group elements. However, other atoms follow the octet rule in most circumstances. Illustrated glossary of organic chemistry octet rule. Dec 03, 2014 a somewhat longer version of the octet rule is this. To print this proof we recommend that you scale the pdf to fit the size. This primarily affects the element hydrogen, which forms stable compounds by achieving two valence electrons.
Everything within our planet is made up of atoms, and it. Principles of chemical science, problems for lecture 11. The octet rule dictates particular electron placement on the orbitals of the atoms nucleus. The octet rule reflects the observation that the most stable ions of many elements have eight electrons in their valence shell for gaining the best possible stability chlorine, for example, typically forms an anion with a charge of. This structure is held responsible for the relative inertness of the noble gases and the chemical behaviour of certain other elements. This lesson discusses why atoms form ions in terms of the octet rule, and how to apply the octet rule in predicting ion formation. The octet rule states that atoms tend to form compounds in ways that give them eight valence electrons and thus the electron configuration of a noble gas. In the formation of a chemical bond, atoms lose, gain or share valence electrons to.
While most elements below atomic number 20 follow the octet rule, several exceptions exist, including compounds of boron and aluminum. The octet rule the other halogen molecules f 2, br 2, i 2, and at 2 form bonds like those in the chlorine molecule. The octet rule states that atoms will lose, gain or share electrons to reach the number of valence electrons of the nearest noble gas. Aug 02, 2011 this lesson discusses why atoms form ions in terms of the octet rule, and how to apply the octet rule in predicting ion formation. The majority of molecules or complex ions discussed in general chemistry courses are demonstrated to have pairs of electrons. Metal atoms will lose electrons to obtain an octet and nonmetals will gain electrons. Lewis symbols represent the resulting structures that accommodate the octet rule. An exception to an octet of electrons is in the case of the first noble gas, helium, which only has two valence electrons. The structure is not legitimate, because the leftmost carbon is missing a lone pair. So in general there are a few ways to tell if you might be dealing with an exception to the octet rule.
Octet rule article about octet rule by the free dictionary. The octet rule is an informal measure of how favorable a chemical bond is between atoms. The octet rule is a chemical rule of thumb that reflects the observation that elements tend to bond in such a way that each atom has eight electrons in its valence. Technically it is less of a worksheet than a detailed explanation of these chemical bonding concepts. Jan 20, 2017 like other rules in chemistry, such as homogeneous and heterogeneous mixtures, the octet rule sounds pretty complex, and it can be difficult to wrap your head around. The octet rule is based on the idea that all atoms on the periodic table eventually want to reach whats called the noble gas configuration. Lithium, an alkali metal with three valence electrons, is also an exception to the octet rule. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens, but also to metals such as sodium or magnesium. Following the octet rule for lewis dot structures leads to the most accurate depictions of stable molecular and atomic structures and because of this we always want to use the octet rule when drawing lewis dot.
In spite of the octet rules many exceptions and limitations, the shared electronpair model is the one that chemists most frequently employ in their daytoday thinking about molecules. Exceptions to the octet rule in those cases where the octet rule does not apply, the substituents attached to the central atom nearly always attain noble gas configurations the central atom does not have a noble gas configuration but may have fewer than 8 or more than 8 electrons. Breaking the octet rule by amanda brindley is licensed under a creative commons attributionsharealike 3. Basically, it states that every atom wants to have eight valence electrons in its outermost electron shell. Low atomic weight elements the first 20 elements are most likely to adhere to the octet rule. This simple rule is completed by a dictionary of nontypical but knownvalid atom environments that is being maintained in the chemistry development kit cdk. If they need go gain electrons so they have this number of electrons, their chemistry will be dominated by this need to gain electrons. This allows each halogen atom to have a noble gas electron configuration, which corresponds to eight valence electrons. In general, the elements that obey this rule include the sblock elements and the pblock elements with the exception of hydrogen, helium, and lithium.
Why elements follow the octet rule atoms follow the octet rule because they always seek the most stable electron configuration. Atoms will do anything within their power to be stable. Exceptions to the octet rule university of illinois. So something like nitric oxide no will have 11 electrons, so there isnt. The concept that compounds containing carbon, nitrogen, oxygen, and fluorine are more stable if these atoms have eight valence electrons. However, it applies to carbon, nitrogen, oxygen, the halogens, and most metals, especially the alkali metals and alkaline earths. The octet rule in chemistry is a chemical rule that explains the rules of atoms, electrons and their forms. Download my free ebook 10 secrets to acing organic chemistry here. Basically, it may state that every atom might want to have eight valence electrons in its outermost electron shell. Hydrogen is excluded because it can hold a maximum of 2 electrons in its valence shell.
It is short and clearly emphasizes the octet rule in atomic structure. The basic formula of the octet rule is straight forward. According to the bohr model, an atom consists of a nucleus of protons and neutrons orbited by a number of electrons. The skit got my students thinking and it led to a lot of discussion about how ions react with each other. Compounds are the result of the formation of chemical bonds between two or more different elements. Anions, cations, and the octet rule all have to do with atoms and their stability. There is also a specially designed lesson meant to help complement this quiz called the octet rule and lewis structures of atoms and you can use this lesson to learn more about this key rule in. Welcome to this mometrix video over anion, cation, and the octet rule. Three cases can be constructed that do not follow the octet rule, and as such, they are known as the exceptions to the octet rule. It was an engaging way to introduce the octet rule. Write the lewis structure, including any equivalent energy resonance structures, for the.
It was named from gilbert newton lewis, who introduced it. I just used the octet rules dating game in my chemistry class last week. Exceptions to the octet rule the le model provides a simple and very successful method for modeling covalent compounds based on the arrangement of atoms and valence electrons, both bonding and nonbonding, resulting in an octet for every atom. A law is a relationship that exists between variables in a group of data. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Video 6 this tutorial video is designed to help new and incoming organic chemistry students build a solid foundation for organic chemistry.
Main groupsmain groups 1 1a periods 2 1 2a 3atransition metal groups14 4a15 5a16 6a17 7a2 33 3b4. The octet rule and periodic trends the cavalcade o chemistry. We explain octet rule with video tutorials and quizzes, using our many waystm approach from multiple teachers. It was named from gilbert newton lewis, who introduced it in 1916. While the octet rule model of atomic structure and chemical bonding has its limitations, its about all the chemistry that a first year biology or even ap biology student needs. Oddelectron molecules represent the first violation to the octet rule. Topics discussed include drawing a lewis dot diagram for atoms, and the octet rule. When one of these atoms has less than eight valence electrons it has an open octet. Octet rules is a short play that describes how atoms interact. So something like nitric oxide no will have 11 electrons, so there isnt any way you can satisfy the octet rule. The attractive force between atoms is informally measured with this rule. Sf6sulfur hexafluoride pcl5phosphorous pentachloride bf3boron trifluoride there are several others similar to. Limitations of octet rule octet rule exceptions chemistry. These molecules, called free radicals, contain at least one unpaired electron, a clear violation of the octet rule.
This gives the atom a valence shell resembling that of a noble gas. A somewhat longer version of the octet rule is this. All right guys, now what i want to do is introduce probably the most important rule in all of chemistry and thats the octet rule. The octet rule is a simple chemical theory that states that atoms tend to combine in such a way that they each have eight electrons in their valence shells, similar to the electronic configuration of a noble gas. Basically, it states that every atom wants to have eight valence electrons in its outermost electron shell background. Following the octet rule results in completely filled s and p orbitals in an atoms outermost energy level. It is a special case of the stability rule of atoms which suggests that the outermost shell should be completely filled for an atom to be stable. From what i have seen, most exceptions to the octet rule involve an multiple atoms of one element from the halogen group. Basically, it may state that every atom might want to have eight valence electrons in its outermost electron shell background.
It also explains how to determine charge and the difference. Alevel chemistry revision science section on octet rule. The octet rule is likely the most useful way in explaining bonding when learning chemistry. Which of the following lewis structures violates the octet rule and is therefore incorrect. Although they are few, some stable compounds have an odd number of electrons in their valence shells. With an odd number of electrons, at least one atom in the molecule will have to violate the octet rule. Here is a topnotch handout to supply your chemistry class with. This lesson will define the octet rule and how this effects an atoms stability. The octet rule song music video sciencemusicvideos. According to this rule, an atom is stable if its outermost shell have total of 8 e. The octet rule is a chemical rule of thumb that reflects the observation that elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. In simple terms, molecules are more stable when the outer shells of their constituent atoms are empty, full, or have a multiple of 8.
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