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

Q: What is the HBr Lewis structure?

HBr Lewis structure is dot representation

Q: What is the formal charge on the HBr Lewis structure?

Zero charges on the HBr molecular structure

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

Table of Contents

Key Points To Consider When Drawing The HBr Electron Dot Structure

A three-step approach for drawing the HBr Lewis structure can be used. The first step is to sketch the Lewis structure of the HBr molecule, to add valence electrons around the bromine 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 HBr Lewis Structure.

The HBr Lewis structure is a diagram that illustrates the number of valence electrons and bond electron pairs in the HBr molecule. The geometry of the HBr molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which states that molecules will choose the HBr 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-Br single bonds (dipole moment properties of the HBr molecule). The hydrogen-bromine bonds in hydrogen bromide(HBr), for example, are polarised toward the more electronegative bromine in HBr 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 bromine atom, their sum of dipole moment is nonzero due to the HBr molecule’s bond dipole moment and less electron polarity to the hydrogen atoms. Because H-Br bonds polarity is not canceled in the HBr molecule due to the presence of three lone pairs of electrons in the tetrahedral structure. The hydrogen bromide(HBr) molecule is classified as a polar molecule.

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

As a result, it has the nonzero dipole moment. The HBr molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges. But both bromine and hydrogen atoms fall on the halogen and hydrogen family groups in the periodic table respectively. The bromine atom is a more electronegative value than hydrogen in the HBr molecule. The HBr molecule has the net dipole moment of 2.60D value in the ground state energy level.

HBr molecule has two H-Br 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 HBr 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: HBr Lewis Structure

The central atom is bromine, which is bordered on two terminals with hydrogen atoms( in tetrahedral or linear geometry), and three lone pairs on the central bromine atom in the tetrahedral or linear molecular geometry. Bromine 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 bromine atom requires one valence electron on each of their outermost shell.

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

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

Lewis structure of HBr has dot electron representative structure. Valence electrons of atoms undergo orbitals mixing in the chemical reactions, gives new types of molecular species of HBr. 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 HBr Molecule:

Bromine and hydrogen Electronegative difference in HBr:

The bromine atom has an electronegativity of 2.96, while hydrogen has an electronegativity of 2.2 in the HBr molecule. The difference in electronegativity of bromine and hydrogen can be estimated using the method below.

The electronegative value difference between bromine and hydrogen in HBr molecule
Electronegativity value of bromine= 2.96
Electronegativity value of hydrogen= 2.20
Difference of electronegativity value between bromine and hydrogen in HBr molecule = 2.96 – 2.20 = 0.76
Electronegativity difference between H-Br bond calculation of HBr molecule

The electronegative difference between bromine and hydrogen is greater than 0.5. This indicated the bond polarity moves near to nonpolar nature. H-Br bond polarity in the HBr molecule is nonpolar.

Because of this difference in electronegativity of bromine and hydrogen atoms, the HBr molecule’s H-Br bond becomes nonpolar. The total net dipole moment of the HBr molecule is nonzero due to the cancellation 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 HBr is discussed in our previous post.

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

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

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

Because three lone pairs on the terminal bromine atoms create interaction with H-Br bond pairs(but it is negligible in the ground state of the HBr molecule). The bond angle of the H-Br bond in the linear or tetrahedral molecular geometry is approximately 180 degrees. This angle is greater than the CH4 molecule bond angle. The H-Br bond length is 141pm(picometer).

To sketch the HBr Lewis structure by following these instructions:

Step-1: HBr Lewis dot Structure by counting valence electrons on the bromine atom

To calculate the valence electron of each atom in HBr, 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 bromine and hydrogen atoms respectively. In their outermost shells, hydrogen and bromine have one and seven valence electrons respectively.

Calculate the total number of valence electrons in the HBr molecule’s outermost valence shell. The first step is to determine how many electrons are in the HBr 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 HBr Lewis diagram. The HBr molecule’s core bromine atom can be represented as follows:

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

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

But in this case, hydrogen is the least electronegative than bromine. Hydrogen takes a maximum of two-electron in its orbital. This gives hydride ion(H-). So that bromine 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 bromine atom as given in the figure.

Step-2: Lewis Structure of HBr for counting valence electrons around the terminal hydrogen atoms

As a result, bromine 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 bromine atom is higher than that of the hydrogen atom in the HBr molecule. Furthermore, hydrogen has a one-electron limit since it is the less electronegative element in the HBr molecule.

In the HBr Lewis structure diagram, the bromine atom can be the center atom of the molecule. As a result, central bromine in the HBr 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 HBr generated from step-1 and step-2

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

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

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

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

The bromine atom in the molecule gets only 8 electrons around its molecular structure. This central bromine atom is octet stable. But it has three lone pairs. Bromine gas(Br2) is a brownish liquid gas. Bromine is very corrosive in nature. It is one of the very reactive chemical reagent.

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.

Bromine requires 8 electrons in its outermost valence shell to complete the molecular octet stability, two electrons bond pairs in one H-Br single bond, and three lone pairs in the central bromine atom. No lone pairs of electrons on the hydrogen atoms of the HBr molecule are placed in a tetrahedral geometry. Bromine already shares 8 electrons to the one H-Br 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 electron.

We’ve positioned 8 electrons around the one-terminal hydrogen atoms(step-3), which is represented by a dot, in the HBr molecular structure above. The bromine atom completes its molecular octet stability in the HBr molecule because it possesses 2 electrons in its (one H-Br 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 HBr Lewis structure. One electron bond pairs are shown as dots in the HBr chemical structure, whereas one single bond contains two electrons. The outermost valence shell electrons of the HBr molecule(bond pairs) are 2 as a result of the calculation. The total valence electron in a bromine atom is 8.

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

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

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

How to calculate the formal charge on bromine and hydrogen atoms in HBr Lewis Structure?

Calculating formal charge on the bromine of HBr molecule:

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

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

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

Formal charge on bromine atom of HBr molecule = (7- 6-(2/2)) =0

In the Lewis structure of HBr, the formal charge on the central bromine atom is zero.

Calculating formal charge on the hydrogen atom of HBr molecule:

The formal charge on the HBr 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 HBr Lewis dot structure.

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

The hydrogen terminal atoms of the HBr 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 HBr molecule = (1- 0-(2/2)) =0

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

Summary:

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