BI3 Lewis Structure, Characteristics: 13 Must-Know Facts

BI3 lewis structure comprises one boron atom and three iodine atoms. It is a very important crystal structure whose complete description is illustrated in this article.

BI3 lewis structure consists of 1 boron surrounded by 3 iodine atoms where boron is the central atom. There is sharing of electrons between both the atom and the formation of 3 B-I covalent bonds. The octet stability of iodine will be satisfied. Boron on the other hand is an exceptional species to it and is octet deficient.

The BI3 lewis structure, also designated as Boron triiodide, is a white crystalline solid compound. Its physical properties show that it has high melting and boiling point of 49.9 degrees Celsius and 210 degrees Celsius respectively. It has a density of 3.35g/ml at 25 degrees Celsius and specific gravity of 3.35.

The BI3 lewis structure is very much soluble in water and is moisture sensitive. It is put under the category of toxic substances due to fierce reactions. It is usually stored in warehouses that are properly ventilated and dry at low temperatures. Special attention is paid to its isolation from other flammable chemicals like ethers, formates, and POCL.

Elaborating on its uses and properties, the BI3 lewis structure is a strong lewis acid and is used in the pharmaceutical and medical industry as a catalyst or organic intermediate to assist various reactions. In the chemical industry or academic laboratory preparation, it acts as a reagent to cleave or dissociate the C-O bond in esters and ethers. Recently BI3 lewis structure has been discovered as a potential catalyst for making nanowires.

Understanding the structure of BI3 lewis structure formation is of utmost significance to understanding its molecular aspects associated with it. The detailed description of its formation is explained below.

How to draw the BI3 lewis structure?

For determining the BI3 lewis structure it is important to calculate the number of valence electrons involved in bonding. BI3 lewis consist of boron (Atomic number = 5 and electronic configuration = 2,3) have 3 valence electrons. Similarly iodine (Atomic number = 53 and electronic configuration = 2,8,18,18,7) from halogen family has 7 valence electrons. So the total number of valence electrons are 3 + 7(3) = 24.

After counting the valence electrons it is important to look out for the central atom which is always the least electronegative atom. In the BI3 lewis structure context boron is the least electronegative atom and the iodine on the other hand belongs to the most electronegative halogen family. Hence boron will be the central atom surrounded by 3 iodine atoms.

Now to complete the octet stability requirement there must be sharing of electrons. Iodine has 7 valence electrons and needs only 1 to complete its noble gas configuration. So there will be the formation of 3 B-I bonds and sharing of 2 electrons. Boron will have 6 electrons instead of 8 electrons after sharing because it is an exception to the octet rule and is an octet deficient species.

Confirming the authenticity and reliability of the BI3 lewis structure is the last step in the structure formation. So the formal charge of each atom involved in the BI3 lewis structure is calculated. The formal charge of both boron and iodine in the BI3 lewis structure is 0 which confirms the existence of the BI3 lewis structure.

There are many properties associated with the BI3 lewis structure which are its foundation. These properties are discussed below:

  1. BI3 lewis structure resonance
  2. BI3 lewis structure shape
  3. BI3 lewis structure formal charge
  4. BI3 lewis structure angle
  5. BI3 lewis structure octet rule
  6. BI3 lewis structure lone pairs
  7. BI3 lewis structure valence electrons
  8. BI3 lewis structure hybridization
  9. BI3 lewis structure solubility
  10. Is BI3 lewis structure ionic?
  11. Is BI3 lewis structure acidic or basic?
  12. Is BI3 lewis structure polar or nonpolar?

BI3 lewis structure resonance

Resonance can be defined as when a single structure is not able to explain all the properties of the molecule and it consists of several hybrid structures called resonating structures. In the case of the BI3 lewis structure, there are no resonating structures because there is the absence of lone pair of electrons on the central atom and the double bonds due to which there is no delocalization and movement.

So the formation of canonical or resonating structures is not possible and only a single structure is responsible for explaining all the properties.

BI3 lewis structure shape

The shape of the BI3 lewis structure can be easily predicted from the lewis structure description. Careful analysis shows that there is a boron atom surrounded by 3 iodine atoms where there is no lone pair of electrons on the boron atom. Hence BI3 lewis structure is of AX3 type molecule which according to VSEPR theory is trigonal planar geometry

2D and 3D representation of BI3 lewis structure geometry

BI3 lewis structure formal charge

The formal charge is calculated to confirm the existence of the lewis structure formed by the arrangement of electrons. The lesser the formal charge the better and more stable the molecule. The formula for calculating the formal charge of an atom is

Formal Charge = Valence electrons – nonbonding electrons – 1/2bonding electrons

FC of iodine in BI3 lewis structure = 7 – 6 – 2/2 = 0

FC of boron in BI3 lewis structure = 3 – 0 – 6/2 = 0 As the formal charge of both the atoms in BI3 lewis structure is 0 hence it is an appropriate and stable structure.

BI3 lewis structure angle

Finding the bond angle of the BI3 lewis structure is pretty much obvious. As already explained above, the BI3 lewis structure is symmetrical and has trigonal planar geometry. So each B-I bond will have a bond angle of 120 degrees.

BI3 lewis structure angle

BI3 lewis structure octet rule

The octet rule is a stability criterion of main-group elements. It says that the valence shell of every element must have 8 electrons for acquiring stability. Most of the atoms in their elemental form do not have 8 valence electrons. So to acquire that they share, gain or lose electrons and bond with the other elements.

In a similar context, the BI3 lewis structure attains octet stability by sharing electrons. Iodine belongs to the halogen family with 7 valence electrons and it shares its 1 electron with boron for completing the octet.

Boron on the flip side is an exception to the octet rule and can have 8 or less than 8 electrons for fulfilling the stability criteria. It is an octet deficient molecule and is stable with 6 valence electrons as shown in BI3 lewis structure.

BI3 lewis structure lone pair

Lone pairs of electrons are those valence electrons that are left behind after the completion of bond formation. They are of great significance and influence many properties of the compound ranging from resonance to molecular shape and bond angle. Another common thing to notice is that the lone pair of central atoms are of importance as compared to terminal atoms as they are the deciding factors for changes in the bond properties

Absence of lone pair in BI3 lewis structure

As far as BI3 lewis structure is concerned then it is a symmetrical molecule and all the valence electrons of boron participated in chemical bond formation leaving 0 lone pair of electrons behind.

BI3 lewis structure valence electrons

Valence electrons are the outermost electrons in the energy levels. Due to greater distance from the central nucleus, they are loosely bound by nuclear forces and can easily participate by sharing, gaining, or losing electrons. In the BI3 lewis structure, boron has 3 valence electrons and iodine has 7 valence electrons. After the formation of boron, triiodide boron has 6 valence electrons and each iodine atom has 8 valence electrons.

BI3 lewis structure hybridization

Hybridization of the BI3 lewis structure can be calculated through its steric number. It is calculated by the addition of no. of bonded atoms attached and the lone pair of electrons over the central atom. Here there are 3 bonded atoms and 0 lone pairs of electrons. Hence bringing all the factors together hybridization of BI3 lewis structure is sp2.

BI3 lewis structure solubility

BI3 lewis structure is soluble in many aqueous and organic solutions. Its solubility is observed with water where it undergoes a hydrolysis reaction. Apart from this, it has solubility in many organic solvents like benzene, CCl4, CS2, benzene, and chloroform.

Is BI3 lewis structure ionic?

No, the BI3 lewis structure is not ionic as there is no loss or gain of electrons. Instead sharing of electrons is there which results in a B-I single covalent bond. Also, boron belongs to the third group of the periodic table so it cannot be defined as complete metal as it shows characteristics of both metals and nonmetals.

Is BI3 lewis structure acid or base?

The properties of boron are intermediate of metals and nonmetals and it shows slightly polar characteristics. Its acidic nature is proved when it reacts with water and forms hydroiodic acid and boric acid. Both of these acids are considered stringent with a pH below 4. As the compound has the capacity of giving one proton, it is justified as acid. Also, various acid-base indicators like the litmus test prove its acidity when they turn red.

Is BI3 lewis structure polar or nonpolar?

BI3 lewis structure is nonpolar. This can be easily explained by its shape which is a symmetrical trigonal planar. Each B-I bond is directed at 120 degrees to each other in a plane canceling the dipole moment. So the net-dipole moment is 0 hence proving its nonpolar nature.


Summarizing the whole article then BI3 lewis structure is a covalent compound which is formed by sharing of electrons between boron and iodine where boron is an exception to the octet rule and is stable as an octet deficient species. Though it is a covalent compound but show slightly polar nature due to intermediate mettaloid character of boron.

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