HF Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for HF molecule?

HF molecular notation is AX1N3.

Hydrogen fluoride or hydrofluoric acid(HF) has the composition of one fluorine and one hydrogen atom. What is the molecular geometry of hydrogen fluoride?. Drawing and predicting the HF molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct HF molecular geometry. fluorine and hydrogen come from the 17th and 1st family groups in the periodic table. Fluorine and hydrogen have seven and one valence electrons respectively.

Table of Contents

Key Points To Consider When drawing The HF Molecular Geometry

A three-step approach for drawing the HF molecular can be used. The first step is to sketch the molecular geometry of the HF molecule, to calculate the lone pairs of the electron in the central fluorine atom; the second step is to calculate the HF hybridization, and the third step is to give perfect notation for the HF molecular geometry.

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

Finally, you must add their bond polarities characteristics to compute the strength of the one H-F single bonds (dipole moment properties of the HF molecular geometry). One hydrogen-fluorine single bonds in the hydrogen fluoride(HF), for example, are polarised toward the more electronegative value fluorine atom, and because (H-F) single bonds have the same size and polarity, their sum is nonzero due to the HF molecule’s bond dipole moment due to pulling the electron cloud to the two side of linear or tetrahedral geometry, and the HF molecule is classified as a polar molecule.

The molecule of hydrogen fluoride(with tetrahedral shape HF molecular geometry) is tilted at 180 degrees bond angle of H-F. It has a difference in electronegativity values between fluorine and hydrogen atoms, with fluorine’s pull the electron cloud being greater than hydrogen’s. But bond polarity of H-F is not canceled to each other in the linear or tetrahedral geometry. As a result, it has a nonzero permanent dipole moment in its molecular structure. The HF molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges in the linear or tetrahedral geometry.

Overview: HF electron and molecular geometry

According to the VSEPR theory, the HF molecule ion possesses linear or tetrahedral molecular geometry. Because the center atom, fluorine, has one H-F single bond with the one hydrogen atom surrounding it. The H-F bond angle is 180 degrees in the tetrahedral HF molecular geometry. The HF molecule has a linear or tetrahedral geometry shape because it contains one hydrogen atom in the tetrahedral and three corners with three lone pairs of electrons.

There is one H-F single bond at the HF molecular geometry. After linking the one hydrogen atom and three lone pairs of electrons on the fluorine atom in the tetrahedral form, it maintains the tetrahedral-shaped structure. In the HF molecular geometry, the H-F single bond has stayed in the one terminal and three lone pairs of electrons on the fluorine atom of the tetrahedral molecule.

The center fluorine atom of HF has three lone pairs of electrons, resulting in tetrahedral HF electron geometry. However, the molecular geometry of HF looks tetrahedral or linear-shaped and has three lone pairs of electrons on the fluorine of the HF geometry. It’s the HF molecule’s slight asymmetrical geometry. As a result, the HF molecule is polar.

How to find HF hybridization and molecular geometry

Calculating lone pairs of electrons on fluorine in the HF geometry:

1.Determine the number of lone pairs of electrons in the core fluorine atom of the HF Lewis structure. Because the lone pairs of electrons on the fluorine atom are mostly responsible for the HF molecule geometry planar, we need to calculate out how many there are on the central fluorine atom of the HF Lewis structure.

Use the formula below to find the lone pair on the fluorine atom of the HF molecule.
L.P(F) = V.E(F) – N.A(H-F)

Lone pair on the central fluorine atom in HF= L.P(F)
The core central fluorine atom’s valence electron in HF = V.E(F)
Number of H-F bond = N.A (H-F)
calculation for fluorine atom lone pair in HF molecule.

For instance of HF, the central atom, fluorine, has seven electrons in its outermost valence shell, one H-F single bond connection. This gives a total of one connection.

As a result of this, L.P(F) = (7 –1)=6

The lone pair of electrons in the fluorine atom of the HF molecule is three.

Calculating lone pair of electrons on hydrogen in the HF geometry:

Finding lone pair of electrons for the terminal hydrogen atom is similar to the central fluorine atom. We use the following formula as given below

Use the formula below to find the lone pair on the hydrogen atom of the HF molecule.
L.P(H) = V.E(H) – N.A(H-F)

Lone pair on the terminal hydrogen atom in HF = L.P(H)
Terminal hydrogen atom’s valence electron in HF= V.E(H)
Number of H-F bonds = N.A ( H-F)
calculation for hydrogen atom lone pair in HF molecule.

For instance of HF, their terminal atoms, hydrogen, have one electron in its outermost valence shell, one H-F single bond connection. This gives a total of one H-F single bond connection. But we are considering only one connection for the calculation.

As a result of this, L.P(H) = (1 –1)=0

The lone pair of electrons in the hydrogen atom of the HF molecule is zero. One hydrogen atom is connected with the central fluorine atom.

In the HF electron geometry structure, the lone pairs on the central fluorine atom are three, lone pairs of electrons in the hydrogen atom have zero. One hydrogen atom has no lone pairs of electrons.

It means there are three lone pairs of electrons in the core fluorine atom. Three lone pair of electrons on the central fluorine atom is responsible for the linear or tetrahedral nature of HF molecular geometry. But in the structure hydrogen atom is polarised sidewise in their linear or tetrahedral geometry.

The three lone pairs of electrons are placed at another side of the HF geometry. Because the hydrogen atom is a lower electronegative value as compared with other atoms in the HF molecule. One hydrogen atom is polarized towards the sidewise in the HF structure.

But in reality, the HF has three lone pairs of electrons in its structure. This makes the HF more asymmetrical in the structure of the molecule. Because there is electric repulsion between bond pairs and lone pairs.

But some sort of interaction is there between hydrogen empty hole and lone pairs of electrons of fluorine of another HF molecule. Here, hydrogen of one molecule acts as an acceptor and fluorine of another molecule as a donor. This is called hydrogen bonding between the two HF molecules. This is one of the main intermolecular forces in HF.

But in the central, fluorine atom has three lone pairs of electrons and these lone pair electrons are placed in the three corners of the tetrahedral.

Calculate the number of molecular hybridizations of the HF molecule

What is HF hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules are made of atoms. In chemistry, atoms are the fundamental particles. There are four different types of orbitals in chemistry. They are named s, p, d, and f orbitals.

The entire periodic table arrangement is based on these orbital theories. Atoms in the periodic table are classified as follows:

s- block elements
p- block elements
d-block elements
f-block elements
Atoms are classified in the periodic table

HF molecule is made of one fluorine and the hydrogen atom. The hydrogen and fluorine atoms have s and p orbitals. But hydrogen atom has only s orbital in the ground state. Hydrogen comes as the first element in the periodic table. The fluorine atom also belongs to the halogen family group. But it falls as the third element in the periodic table.

When these atoms combine to form the HF molecule, its atomic orbitals are mixed and form unique molecular orbitals due to hybridization.

How do you find the HF molecule’s hybridization? We must now determine the molecular hybridization number of HF.

The formula of HF molecular hybridization is as follows:
No. Hyb of HF= N.A(H-F bond) + L.P(F)
No. Hy of HF= the number of hybridizations of HF
Number of H-F bonds = N.A (H-F bonds)
Lone pair on the central fluorine atom = L.P(F)
Calculation for hybridization number for HF molecule

In the HF molecule, fluorine is a core central atom with one hydrogen atom connected to it. It has three lone pairs of electrons on fluorine. The number of HF hybridizations (No. Hyb of HF) can then be estimated using the formula below.

No. Hyb of HF= 3+1=4

The HF molecule ion hybridization is four. The fluorine and hydrogen atoms have s and p orbitals. The sp3 hybridization of the HF molecule is formed when one s orbital and three p orbitals join together to form the HF molecular orbital.

Molecular Geometry Notation for HF Molecule :

Determine the form of HF molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the HF molecule.

The AXN notation of HF molecule is as follows:
The central fluorine atom in the HF molecule is denoted by the letter A.
The bound pairs (one H-F bond) of electrons to the core fluorine atom are represented by X.
The lone pairs of electrons on the central fluorine atom are denoted by the letter N.
Notation for HF molecular geometry

We know that HF is the core atom, with one electron pair bound (one H-F) and three lone pairs of electrons. The general molecular geometry formula for HF is AX1N3.

According to the VSEPR theory, if the HF molecule ion has an AX1N3 generic formula, the molecular geometry and electron geometry will both be tetrahedral or linear-shaped forms.

Name of Molecule	Hydrogen fluoride
Chemical molecular formula	HF
Molecular geometry of HF	Tetrahedral or linear
Electron geometry of HF	Tetrahedral or linear
Hybridization of HF	sp3
Bond angle (H-F)	180º degree
Total Valence electron for HF	8
The formal charge of HF on fluorine	0

Summary:

In this post, we discussed the method to construct HF molecular geometry, the method to find the lone pairs of electrons in the central HF atom, HF hybridization, and HF molecular notation. Need to remember that, if you follow the above-said method, you can construct the HF molecular structure very easily.