Valency of fluorine is 1. Since the atomic number of fluorine is 9 so it has 7 electrons in its valence shell and need just 1 electron to fill it's valence shell and attain noble gas configuration. So valency of fluorine. For example, the characterization of the valence shell charge concentration (VSCC) of the fluorine atom in its compounds through AIM theory provides a simple explanation for the weakness of the F–F bond in F 2, which is explained traditionally by the repulsion between the lone-pairs of each fluorine atom.

Find out the total number of valence electrons in PF3, which is 26. Find out the number of valence electrons further needed of a single PF3 molecule to stabilize itself. It is six in total, where three valence electrons are needed by the phosphorus atom and one, each by three fluorine atoms. For example, fluorine has seven valence electrons, so it is most likely to gain one electron to form an ion with a 1- charge. We can use this method to predict the charges of ions in ionic compounds. When forming ions, elements typically gain or lose the minimum number of electrons necessary to achieve a full octet.

Learning Objectives

• Define valence bond theory.
• Describe how to use valence bond theory to explain aspects of covalent bonds.

What happens next?

We have seen that the old fish-hook idea of atoms connecting that Democritus liked so much just doesn’t work. Electrons don’t have little hooks on them, but they are the basis for connecting atoms to form molecules. You have learned how to write Lewis electron-dot structures for molecules and predict their shape using VSEPR theory. Now it is time to apply these abilities to understand how the electrons behave in their atomic orbitals when a covalent bond forms.

Valence Bond Theory

You have learned that a covalent bond forms when the electron clouds of two atoms overlap with each other. In a simple H ₂ molecule, the single electron in each atom becomes attracted to the nucleus of the other atom in the molecule as the atoms come closer together. An optimum distance, equal to the bond length, is eventually attained, and the potential energy reaches a minimum. A stable, single covalent bond has formed between the two hydrogen atoms. Other covalent bonds form in the same way as unpaired electrons from two atoms “match up” to form the bond. In a fluorine atom, there is an unpaired electron in one of the 2p orbitals. When a F ₂ molecule forms, the 2p orbitals from each of the two atoms overlap to produce the F−F covalent bond. The overlapping orbitals do not have to be of the same type. In a molecule of HF, the 1s orbital of the hydrogen atom overlaps with the 2p orbital of the fluorine atom (see figure below).

In essence, any covalent bond results from the overlap of atomic orbitals. This idea forms the basis for a quantum mechanical theory called valence bond (VB) theory. In valence bond theory , the electrons in a molecule are assumed to occupy atomic orbitals of the individual atoms and a bond results from overlap of those orbitals.

Summary

• Electrons occupy atomic orbitals.
• Covalent bonds result from the overlap of atomic orbitals.

Practice

View the presentation at the link below and take the quizzes.

Review

1. Where are electrons according to valence bond theory?
2. How do covalent bonds form?
3. Do the orbitals of the two electrons involved in the bond need to be the same?

Glossary

• valence bond theory: The electrons in a molecule are assumed to occupy atomic orbitals of the individual atoms and a bond results from overlap of those orbitals.

References

1. CK-12 Foundation – Jodi So.
2. CK-12 Foundation – Jodi So. CK-12 Foundation.

Fluorine (F) is the first element in the Halogen group (group 17) in the periodic table. Its atomic number is 9 and its atomic weight is 19, and it's a gas at room temperature. It is the most electronegative element, given that it is the top element in the Halogen Group, and therefore is very reactive. It is a nonmetal, and is one of the few elements that can form diatomic molecules (F2). It has 5 valence electrons in the 2p level. Its electron configuration is 1s²2s²2p⁵. It will usually form the anion F^- since it is extremely electronegative and a strong oxidizing agent. Fluorine is a Lewis acid in weak acid, which means that it accepts electrons when reacting. Fluorine has many isotopes, but the only stable one found in nature is F-19.

Quick Reference Table

Fluorine Valence Charge

Brief History

In the late 1600's minerals which we now know contain fluorine were used in etching glass. The discovery of the element was prompted by the search for the chemical substance which was able to attack glass (it is HF, a weak acid). The early history of the isolation and work with fluorine and hydrogen fluoride is filled with accidents since both are extremely dangerous. Eventually, electrolysis of a mixture of KF and HF (carefully ensuring that the resulting hydrogen and fluorine would not come in contact) in a platinum apparatus yielded the element.

Fluorine was discovered in 1530 by Georgius Agricola. He originally found it in the compound Fluorspar, which was used to promote the fusion of metals. It was under this application until 1670, when Schwanhard discovered its usefulness in etching glass. Pure fluorine (from the Latin fluere, for 'flow') was was not isolated until 1886 by Henri Moissan, burning and even killing many scientists along the way. It has many uses today, a particular one being used in the Manhattan project to help create the first nuclear bomb.

Electronegativity of Fluorine

Fluorine is the most electronegative element on the periodic table, which means that it is a very strong oxidizing agent and accepts other elements' electrons. Fluorine's atomic electron configuration is 1s²2s²2p⁵. (see Figure 2)

Fluorine is the most electronegative element because it has 5 electrons in it's 2P shell. The optimal electron configuration of the 2P orbital contains 6 electrons, so since Fluorine is so close to ideal electron configuration, the electrons are held very tightly to the nucleus. The high electronegativity of fluorine explains its small radius because the positive protons have a very strong attraction to the negative electrons, holding them closer to the nucleus than the bigger and less electronegative elements.

Reactions of Fluorine

Because of its reactivity, elemental fluorine is never found in nature and no other chemical element can displace fluorine from its compounds. Fluorine bonds with almost any element, both metals and nonmetals, because it is a very strong oxidizing agent. It is very unstable and reactive since it is so close to its ideal electron configuration. It forms covalent bonds with nonmetals, and since it is the most electronegative element, is always going to be the element that is reduced. It can also form a diatomic element with itself ((F_2)), or covalent bonds where it oxidizes other halogens ((ClF), (ClF_3), (ClF_5)). It will react explosively with many elements and compounds such as Hydrogen and water. Elemental Fluorine is slightly basic, which means that when it reacts with water it forms (OH^-).

[3F_2+2H_2O rightarrow O_2+4HF tag{1}]

When combined with Hydrogen, Fluorine forms Hydrofluoric acid ((HF)), which is a weak acid. This acid is very dangerous and when dissociated can cause severe damage to the body because while it may not be painful initially, it passes through tissues quickly and can cause deep burns that interfere with nerve function.

[HF+H_2O rightarrow H_3O^++F^- tag{2}]

There are also some organic compounds made of Fluorine, ranging from nontoxic to highly toxic. Fluorine forms covalent bonds with Carbon, which sometimes form into stable aromatic rings. When Carbon reacts with Fluorine the reaction is complex and forms a mixture of (CF_4), (C_2F_6), an (C_5F_{12}).

[C_{(s)} + F_{2(g)} rightarrow CF_{4(g)} + C_2F_6 + C_5F_{12} tag{3}]

Fluorine reacts with Oxygen to form (OF_2) because Fluorine is more electronegative than Oxygen. The reaction goes:

[2F_2 + O_2 rightarrow 2OF_2 tag{4}]

Fluorine is so electronegative that sometimes it will even form molecules with noble gases like Xenon, such as the the molecule Xenon Difluoride, (XeF_2).

[Xe + F_2 rightarrow XeF_2 tag{5}]

Fluorine also forms strong ionic compounds with metals. Some common ionic reactions of Fluorine are:

[F_2 + 2NaOH rightarrow O_2 + 2NaF +H_2 tag{6}]

[4F_2 + HCl + H_2O rightarrow 3HF + OF_2 + ClF_3 tag{7}]

[F_2 + 2HNO_3 rightarrow 2NO_3F + H_2 tag{8}]

Applications of Fluorine

Compounds of fluorine are present in fluoridated toothpaste and in many municipal water systems where they help to prevent tooth decay. And, of course, fluorocarbons such as Teflon have made a major impact on life in the 20th century. There are many applications of fluorine:

Fluorine Valence Electrons Number

• Rocket fuels
• Polymer and plastics production
• teflon and tefzel production
• When combined with Oxygen, used as a refrigerator cooler
• Hydrofluoric acid used for glass etching
• Purify public water supplies
• Uranium production
• Air conditioning

Sources

Fluorine can either be found in nature or produced in a lab. To make it in a lab, compounds like Potassium Fluoride are put through electrolysis with Hydrofluoric acid to create pure Fluorine and other compounds. It can be carried out with a variety of compounds, usually ionic ones involving Fluorine and a metal. Fluorine can also be found in nature in various minerals and compounds. The two main compounds it can be found in are Fluorspar ((CaF_2)) and Cryolite ((Na_3AlF_6)).

References

1. Newth, G. S. Inorganic Chemistry. Longmans, Green, and Co.:New York, 1903.
2. Latimer, Wendell M., Hildebrand, Joel H. Reference Book of Inorganic Chemistry. The Macmillan Company: New York, 1938.

Problems

(Highlight to view answers)

1. Q. What is the electron configuration of Fluorine? of F^-?

A. 1s²2s²2p⁵

1s²2s²2p⁶

2. Q. Is Fluorine usually oxidized or reduced? explain.

A. Fluorine is usually reduced because it accepts an electron from other elements since it is so electronegative.

3. Q. What are some common uses of Fluorine?

A. Toothpaste, plastics, rocket fuels, glass etching, etc.

4. Q. Does Fluorine form compounds with nonmetals? if so, give two examples, one of them being of an oxide.

A. OF₂, ClF

Fluorine Number Of Valence Electron

5. Q. What group is Fluorine in? (include name of group and number)

Fluorine Valence Number

A. 17, Halogens

Contributors and Attributions

• Rachel Feldman (University of California, Davis)

• Stephen R. Marsden