How to draw HF Lewis Structure? - Science Education and Tutorials

The hydrogen fluoride or hydrofluoric acid chemical formula is HF. Drawing HF Lewis Structure is very easy to by using the following method. Here in this post, we described step by step method to construct HF Lewis Structure. The fluorine and hydrogen elements come as the member of the halogen and hydrogen family groups from the periodic table respectively. The valence electrons in fluorine and hydrogen are seven and one respectively. Hydrogen fluoride is used to make chemical reagents for organic chemical reactions as a catalyst or reagent in organic chemistry.

Table of Contents

Key Points To Consider When Drawing The HF Electron Dot Structure

A three-step approach for drawing the HF Lewis structure can be used. The first step is to sketch the Lewis structure of the HF molecule, to add valence electrons around the fluorine atom; the second step is to add valence electrons to the one hydrogen atom, and the final step is to combine the step1 and step2 to get the HF Lewis Structure.

The HF Lewis structure is a diagram that illustrates the number of valence electrons and bond electron pairs in the HF molecule. The geometry of the HF molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which states that molecules will choose the HF geometrical shape in which the electrons have from one another.

Finally, you must add their bond polarities to compute the strength of the one H-F single bonds (dipole moment properties of the HF molecule). The hydrogen-fluorine bonds in hydrogen fluoride(HF), for example, are polarised toward the more electronegative fluorine in HF molecule, and because both bonds have the same size and are located around one hydrogen terminal of the tetrahedral or linear structure with three lone pairs (in total six electrons) on the fluorine atom, their sum of dipole moment is nonzero due to the HF molecule’s bond dipole moment and less electron polarity to the hydrogen atoms. Because H-F bonds polarity is not canceled in the HF molecule due to the presence of three lone pairs of electrons in the tetrahedral structure. The hydrogen fluoride(HF) molecule is classified as a polar molecule.

The molecule of hydrogen fluoride(with tetrahedral or linear-shaped molecular geometry) is tilted, the bond angles between fluorine and hydrogen are 180 degrees. It has a difference in electronegativity values between fluorine and hydrogen atoms, with central fluorine’s pull being higher than terminal hydrogen’s in the HF molecule. But they not canceled each other due to the asymmetrical tetrahedral with three lone pairs in the molecular geometry of the HF molecule.

As a result, it has the nonzero dipole moment. The HF molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges. But both fluorine and hydrogen atoms fall on the halogen and hydrogen family groups in the periodic table respectively. The fluorine atom is a more electronegative value than hydrogen in the HF molecule. The HF molecule has the net dipole moment of 1.08D value in the ground state energy level.

HF molecule has two H-F single bonds. Its dipole moment in the ground state is totally different as compared with the excited state. If it absorbs light may be from visible or UV light. It undergoes pi to pi star and n to pi star transition from ground state energy level to excited state energy level. In the excited state energy level, the HF molecule shows a definite dipole moment. But it is very dynamic in nature.

Molecules can be classified as polar or nonpolar. The molecule polar behaves in a different manner as compared to nonpolar.

Overview: HF Lewis Structure

The central atom is fluorine, which is bordered on two terminals with hydrogen atoms( in tetrahedral or linear geometry), and three lone pairs on the central fluorine atom in the tetrahedral or linear molecular geometry. Fluorine has seven outermost valence electrons, indicating that it possesses seven electrons in its outermost shell, whereas hydrogen also has one valence electron in its outermost shell. To complete the octet of the fluorine atom requires one valence electron on each of their outermost shell.

One hydrogen atom establishes covalent connections with the central fluorine atom as a result, leaving the fluorine atom with three lone pairs. There are three lone pairs of electrons on the fluorine central atom that resists the bond pairs of the H-F bond. According to VSEPR theory, the H-F bond pairs polarity lead the HF molecule to take on the linear or tetrahedral geometry structure.

The HF molecule’s two H-F bonds are arranged in asymmetrical polarity order around the linear or tetrahedral molecular geometry, giving rise to the HF molecular shape. The HF molecule has a tetrahedral or linear molecular geometry because there is an electrical repulsion between the lone pairs of electrons in fluorine and one single bond pair(H-F) of the HF molecule.

Lewis structure of HF has dot electron representative structure. Valence electrons of atoms undergo orbitals mixing in the chemical reactions, gives new types of molecular species of HF. The molecule is nothing but a bundle of valence electrons from the atoms. But it is converted to bond pairs and lone pairs in the molecular structure.

Electronegative value Difference Calculation of HF Molecule:

Fluorine and hydrogen Electronegative difference in HF:

The fluorine atom has an electronegativity of 3.98, while hydrogen has an electronegativity of 2.2 in the HF molecule. The difference in electronegativity of fluorine and hydrogen can be estimated using the method below.

The electronegative value difference between fluorine and hydrogen in HF molecule
Electronegativity value of fluorine= 3.98
Electronegativity value of hydrogen= 2.20
Difference of electronegativity value between fluorine and hydrogen in HF molecule = 3.16 – 2.20 = 1.78
Electronegativity difference between H-F bond calculation of HF molecule

The electronegative difference between fluorine and hydrogen is greater than 0.5. This indicated the bond polarity moves polar nature. H-F bond polarity in the HF molecule is polar.

Because of this difference in electronegativity of fluorine and hydrogen atoms, the HF molecule’s H-F bond becomes polar in nature. The total net dipole moment of the HF molecule is nonzero due to the noncancellation of the bond dipole moment in the linear or tetrahedral geometry due to the presence of three lone pairs of electrons. The electronegativity of an atom is the strength with which it may attract bound electron pairs to its side. The polarity of HF is discussed in our previous post.

As a result, the H-F bond’s dipole moment is higher due to the polarization of the bonds and three lone pairs of electrons on fluorine, and all H-F bonds’ dipoles are arranged in the asymmetrical HF molecular geometry. The HF molecule has a nonzero net dipole moment.

The electron dot structure of the HF molecule is also known as the HF Lewis structure. It determines the number of outermost valence electrons as well as the electrons engaged in the HF molecule’s bond formation. The outermost valence electrons of the HF molecule must be understood while constructing the Lewis structure of the molecule.

The fluorine atom is the middle element in HF molecular geometry, with seven electrons in its outermost valence electron shell, whereas the hydrogen atom has one electron in its outermost valence electron shell. The hydrogen atom has one valence electron.

The HF has a total of 8 valence electrons as a result of the foregoing above-said reasoning. With the core central fluorine atom, the one terminals with one hydrogen atom form covalent bonds, leaving the fluorine atom with three lone pairs in the middle of linear or tetrahedral geometry.

Because three lone pairs on the terminal fluorine atoms create interaction with H-F bond pairs(but it is negligible in the ground state of the HF molecule). The bond angle of the H-F bond in the linear or tetrahedral molecular geometry is approximately 180 degrees. This angle is greater than the CH4 molecule bond angle. The H-F bond length is 91pm(picometer).

To sketch the HF Lewis structure by following these instructions:

Step-1: HF Lewis dot Structure by counting valence electrons on the fluorine atom

To calculate the valence electron of each atom in HF, look for its periodic group from the periodic table. The halogen and hydrogen group families, which are the 17th and 1st groups in the periodic table, are both made up of fluorine and hydrogen atoms respectively. In their outermost shells, hydrogen and fluorine have one and seven valence electrons respectively.

Calculate the total number of valence electrons in the HF molecule’s outermost valence shell. The first step is to determine how many electrons are in the HF Lewis structure’s outermost valence shell. An electron in an atom’s outermost shell is known as a valence electron. It is represented by dots in the HF Lewis diagram. The HF molecule’s core fluorine atom can be represented as follows:

Total outermost valence shell electron of fluorine atom in HF= 7
Total outermost valence shell electron of hydrogen atom in HF= 1
The HF molecule has one central fluorine and one hydrogen atoms. Then the total outermost valence shell electrons can be calculated as follows
∴ Total outermost valence shell electrons available for HF Lewis structure( dot structure) = 7+1*1= 8 valence electrons in HF.
calculation of total valence electron of HF molecule

Choose the atom with the least electronegative value atom and insert it in the center of the molecular geometry of HF. We’ll choose the least electronegative value atom in the HF molecule to place in the center of the HF Lewis structure diagram in this phase.

But in this case, hydrogen is the least electronegative than fluorine. Hydrogen takes a maximum of two-electron in its orbital. This gives hydride ion(H-). So that fluorine stays in the central molecular structure. The electronegativity value in periodic groups grows from left to right in the periodic table and drops from top to bottom.

The first step is to put seven valence electrons around the fluorine atom as given in the figure.

Step-2: Lewis Structure of HF for counting valence electrons around the terminal hydrogen atom

As a result, fluorine is the first atom in the periodic table’s halogen family group. Hydrogen is the first member of the hydrogen family. It is the first element in the periodic table. The electronegative value of the fluorine atom is higher than that of the hydrogen atom in the HF molecule. Furthermore, hydrogen has a one-electron limit since it is the less electronegative element in the HF molecule.

In the HF Lewis structure diagram, the fluorine atom can be the center atom of the molecule. As a result, central fluorine in the HF Lewis structure, with one hydrogen atom arranged in a linear or tetrahedral geometry.

Add valence electron around the hydrogen atom, as given in the figure.

Step-3: Lewis dot Structure for HF generated from step-1 and step-2

Connect the exterior and core central atom of the HF molecule with one single H-F bond. In this stage, use one hydrogen atom on the outside of the HF molecule to the central fluorine atom in the middle.

Count how many electrons from the outermost valence shell have been used in the HF structure so far. H-F single bond carries two electrons because the fluorine atom is connected to one hydrogen atom by H-F single bonds. Bond pairings of H-F are what they’re called.

So, out of the total of 8 valence electrons available for the HF Lewis structure, we used four electrons for the HF molecule’s one H-F single bond. The HF molecule has three lone pairs of electrons in the central fluorine atom.

Place the valence electrons in the H-F bond pair starting with the core fluorine, one hydrogen atom in the HF molecule. In the HF Lewis structure diagram, we always begin by introducing valence electrons from the central fluorine atom(in step1). As a result, wrap around the central fluorine atom’s bond pair valence electrons first (see figure for step1).

The fluorine atom in the molecule gets only 8 electrons around its molecular structure. This central fluorine atom is octet stable. But it has three lone pairs. Fluorine gas(Cl2) is a gas. Fluorine is very corrosive in nature. It is one of the very reactive chemical reagents for many chemical reactions.

Hydrogen molecule(H2) is in the gaseous state at normal temperature and pressure. It is used as a hydrogenating agent in the field of organic chemistry. It is highly flammable in nature. It is applied in fuel cells. During the combustion, hydrogen gas gives the stream as the final product. This reduces environmental pollution.

Fluorine requires 8 electrons in its outermost valence shell to complete the molecular octet stability, two electrons bond pairs in one H-F single bond, and three lone pairs in the central fluorine atom. No lone pairs of electrons on the hydrogen atoms of the HF molecule are placed in a linear or tetrahedral geometry. Fluorine already shares 8 electrons to the one H-F single bonds. Then place the valence electron in the hydrogen atoms, it placed around one electron on each atom(step-2). There are no valence electrons placed around one hydrogen atom as lone pair of electrons.

We’ve positioned 8 electrons around the one-terminal hydrogen atoms(step-3), which is represented by a dot, in the HF molecular structure above. The fluorine atom completes its molecular octet stability in the HF molecule because it possesses 2 electrons in its (one H-F single bonds) bond pairs with one hydrogen in the outermost valence shell.

Count how many outermost valence shell electrons have been used so far using the HF Lewis structure. One electron bond pairs are shown as dots in the HF chemical structure, whereas one single bond contains two electrons. The outermost valence shell electrons of the HF molecule(bond pairs) are 2 as a result of the calculation. The total valence electron in a fluorine atom is 8.

So far, we’ve used 8 of the HF Lewis structure’s total 8 outermost valence shell electrons. Three lone pairs of electrons on the fluorine atom in the linear or tetrahedral geometry of the HF molecule.

Complete the middle HF atom stability and, if necessary, apply a covalent bond. The central fluorine atom undergoes octet stability(due to one single bond pair of electrons).

The core atom in the HF Lewis structure is fluorine, which is bonded to the one hydrogen atom by single bonds (one H-F). With the help of one single bond, it already shares 8 electrons. As a result, the fluorine follows the octet rule and has 8 electrons surrounding it on the one terminal of the HF molecule’s linear or tetrahedral geometry.

How to calculate the formal charge on fluorine and hydrogen atoms in HF Lewis Structure?

Calculating formal charge on the fluorine of HF molecule:

The formal charge on the HF molecule’s fluorine central atom often corresponds to the actual charge on that fluorine central atom. In the following computation, the formal charge will be calculated on the central fluorine atom of the HF Lewis dot structure.

To calculate the formal charge on the central fluorine atom of the HF molecule by using the following formula:
The formal charge on the fluorine atom of HF molecule= (V. E(F)– L.E(F) – 1/2(B.E))
V.E (F) = Valence electron in a fluorine atom of HF molecule
L.E(F) = Lone pairs of an electron in the fluorine atom of the HFmolecule.
B.E = Bond pair electron in F atom of HF molecule
calculation of formal charge on fluorine atom in HF molecule

The fluorine core atom (one single bond connected to one hydrogen atom) of the HF molecule has seven valence electrons, three lone pairs of electrons(six electrons), and 2 bonding pairing valence electrons. Put these values for the fluorine atom in the formula above.

Formal charge on fluorine atom of HF molecule = (7- 6-(2/2)) =0

In the Lewis structure of HF, the formal charge on the central fluorine atom is zero.

Calculating formal charge on the hydrogen atom of HF molecule:

The formal charge on the HF molecule’s hydrogen terminal atoms often corresponds to the actual charge on that hydrogen terminal atoms. In the following computation, the formal charge will be calculated on the terminal hydrogen atom of the HF Lewis dot structure.

To calculate the formal charge on the terminal hydrogen atom of the HF molecule by using the following formula:
The formal charge on the hydrogen atom of HF molecule= (V. E(H)– L.E(H) – 1/2(B.E))
V.E (H) = Valence electron in a hydrogen atom of HF molecule
L.E(H) = Lone pairs of an electron in the hydrogen atom of the HF molecule.
B.E = Bond pair electron in H atom of HF molecule
calculation of formal charge on hydrogen atom in HF molecule

The hydrogen terminal atoms of the HF molecule have one valence electron, no lone pairs of electrons(zero electrons), and two bonding pairing valence electrons(single bond). Put these values for the hydrogen atom in the formula above.

Formal charge on hydrogen atom of HF molecule = (1- 0-(2/2)) =0

In the Lewis structure of HF, the formal charge on the terminal hydrogen atom is zero.

Summary:

In this post, we discussed the method to construct the HF Lewis structure. First, the valence electrons are placed around the fluorine atom. Second, place the valence electron on the hydrogen atom. Finally, when we combined the first and second steps. It gives HF Lewis structure. Need to remember that, if you follow the above-said method, you can construct molecular dot structure very easily.