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

The potassium bromide chemical formula is KBr. Drawing KBr Lewis Structure is very easy to by using the following method. Here in this post, we described step by step method to construct KBr Lewis Structure. The bromine and potassium elements come as members of the halogen and alkaline metal family groups from the periodic table respectively. The valence electrons in bromine and potassium are seven and one respectively. Potassium 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 KBr Electron Dot Structure

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

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

Finally, you must add their bond polarities to compute the strength of the one K+—Br- single bonds (dipole moment properties of the KBr molecule). The potassium-bromine ionic bonds in potassium bromide(KBr), for example, are polarised toward the more electronegative bromine in KBr molecule, and because both bonds have the same size and are located around one potassium terminal of the linear structure with three lone pairs (in total eight electrons) on the bromine atom as bromide ion(Br-), their sum of dipole moment is nonzero due to the KBr molecule’s bond dipole moment and less electron polarity to the potassium atoms and become potassium ion. Because K+—-Br- bonds polarity is not canceled in the KBr molecule due to the presence of four lone pairs of electrons in the linear structure. The potassium bromide(KBr) molecule is classified as a polar ionic molecular crystal.

The molecule of potassium bromide(linear-shaped molecular geometry) is tilted, the bond angles between bromine (as bromide ion) and potassium (as potassium ion) are 180 degrees. It has a difference in electronegativity values between bromine and potassium atoms, with central bromine’s pull being higher than terminal potassium’s in the KBr ionic molecule. But they do not cancel each other due to the linear structure with four lone pairs in the molecular geometry of the KBr molecule.

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

KBr molecule has one K+—–Br- single bond. 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 KBr ionic 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: KBr Lewis Structure

The central atom is bromine, which is bordered on two terminals with potassium atoms(linear structural geometry), and four lone pairs on the central bromine atom in the linear molecular geometry. Bromine has seven outermost valence electrons, indicating that it possesses seven electrons in its outermost shell, whereas potassium 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 potassium 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 K+—-Br- bond. According to VSEPR theory, the K+—-Br- ionic bond pairs polarity lead the KBr molecule to take on the linear geometry structure.

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

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

Electronegative value Difference Calculation of KBr Molecule:

Bromine and potassium Electronegative difference in KBr:

The bromine atom has an electronegativity of 2.96, while potassium has an electronegativity of 0.82 in the KBr ionic molecule. The difference in electronegativity of bromine and potassium can be estimated using the method below.

The electronegative value difference between bromine and potassium in KBr molecule
Electronegativity value of bromine= 2.96
Electronegativity value of potassium= 0.82
Difference of electronegativity value between bromine and potassium in KBr molecule = 2.96 – 0.82 = 2.14
Electronegativity difference between K-Br ionic bond calculation of KBr molecule

The electronegative difference between bromine and potassium is greater than 0.5. This indicated the bond polarity moves near to polar nature. K-Br ionic bond polarity in the KBr molecule is polar.

Because of this difference in electronegativity of bromine and potassium atoms, the KBr molecule’s K+—Br- bond becomes nonpolar. The total net dipole moment of the KBr molecule is nonzero due to the cancellation of the bond dipole moment in the linear 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.

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

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

The bromine atom is the middle element in KBr molecular geometry, with seven electrons in its outermost valence electron shell, whereas the potassium atom has one electron in its outermost valence electron shell. The potassium atom has one valence electron.

The KBr 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 potassium atom form ionic bonds, leaving the bromine atom with four lone pairs in the middle of linear geometry.

Because three lone pairs on the terminal bromine atoms create interaction with K-Br bond pairs(but it is negligible in the ground state of the KBr molecule). The bond angle of the K-Br bond in the linear molecular geometry is approximately 180 degrees. This angle is greater than the CH4 molecule bond angle. The K-Br bond length is 250 pm(picometer).

To sketch the KBr Lewis structure by following these instructions:

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

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

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

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

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

But in this case, potassium is the least electronegative than bromine. Potassium loses one electron and forms potassium positive ions(K+). 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 potassium atom as given in the figure.

Step-2: Lewis Structure of KBr for counting valence electrons around the terminal potassium atoms

As a result, bromine is the third atom in the periodic table’s halogen family group. Potassium is the first member of the alkaline metal family. It is the fourth element in the periodic table. The electronegative value of the bromine atom is higher than that of the potassium atom in the KBr molecule. Furthermore, potassium has a one-electron limit since it is the less electronegative element in the KBr molecule.

In the KBr Lewis structure diagram, the bromine atom can be the center atom of the molecule. As a result, central bromine in the KBr Lewis structure, with one potassium atom arranged in a linear geometry.

Bromine accepts one electron and forms a bromide ion(Br-). The total lone pair of electrons in the bromide ion is eight. They are negatively charged.

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

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

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

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

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

Place the valence electrons in the K-Br bond pair starting with the core bromine, one potassium atom in the KBr molecule. In the KBr Lewis structure diagram, we always begin by introducing valence electrons from the central bromine atom(in step 2). As a result, wrap around the central bromine atom’s bond pair valence electrons first (see figure for step2).

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 reagents.

Potassium metal is in a soft solid state at normal temperature and pressure. It is used as a reducing agent in the field of organic chemistry. It is highly flammable in nature. It is very reactive in water and alcohol. Water reacts with potassium metal and forms potassium hydroxide. Similarly, alcohol(such as methanol) reacted with potassium and forms potassium methoxide.

Bromine requires 8 electrons in its outermost valence shell to complete the molecular octet stability, two electrons bond pairs in one K-Br single bond, and three lone pairs in the central bromine atom. No lone pairs of electrons on the potassium atoms of the KBr molecule are placed in a linear geometry. Bromine already shares 8 electrons to the one K-Br single bonds. Then place the valence electron in the potassium atoms, it placed around one electron on each atom(step-1). There are no valence electrons placed around one potassium atom as lone pair of electrons.

We’ve positioned 8 electrons around the one-terminal potassium atoms(step-3), which is represented by a dot, in the KBr molecular structure above. The bromine atom completes its molecular octet stability in the KBr molecule because it possesses 2 electrons in its (one K-Br single ionic bond pairs) bond pairs with one potassium in the outermost valence shell.

Count how many outermost valence shell electrons have been used so far using the KBr Lewis structure. One electron bond pairs are shown as dots in the KBr chemical structure, whereas one single bond contains two electrons. The outermost valence shell electrons of the KBr 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 KBr 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 KBr molecule.

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

The core atom in the KBr Lewis structure is bromine, which is bonded to the one potassium atom by single bonds (one K-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 KBr molecule’s linear or tetrahedral geometry.

How to calculate the formal charge on bromine and potassium atoms in KBr Lewis Structure?

Calculating formal charge on the bromine of KBr molecule:

The formal charge on the KBr 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 KBr Lewis dot structure.

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

The bromine core atom (one single bond connected to one potassium atom) of the KBr 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 KBr molecule = (7- 8-(0/2)) = -1

In the Lewis structure of KBr, the formal charge on the central bromine atom is -1 (negative charge).

Calculating formal charge on the potassium atom of KBr molecule:

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

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

The potassium terminal atoms of the KBr 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 potassium atom in the formula above.

Formal charge on potassium atom of KBr molecule = (1- 0-(0/2)) =+1

In the Lewis structure of KBr, the formal charge on the terminal potassium atom is +1 (positive charge).

Summary:

In this post, we discussed the method to construct the KBr Lewis structure. First, the valence electrons are placed around the potassium atom and lose one electron. Then it becomes potassium positive ions. Second, place the valence electron on the bromine atoms and the bromine atom accepts one electron in its valence shell. Finally, when we combined the first and second steps. It gives KBr Lewis structure. Need to remember that, if you follow the above-said method, you can construct molecular dot structure very easily.