What Is Triiodide?

Triiodide in Chemistry usually refers to the triiodide ion, I3- This anion, among the polyhalogen ions, is composed of 3 iodine atoms and also is created by combine the aqueous systems of iodine and iodide salts. A few salts the the anion have actually been isolated, including ammonium triiodide (+− and also thallium(I) triiodide (Tl+−)). The triiodide is well-known to it is in red colour in solution.

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What Is The Hybridization that Triiodide Ion?

To recognize the hybridization of any kind of molecule, over there is a simple formula that can be used. This formula is used to find out the hybridization number, which help in discovering the molecule hybridization.

The hybrid numbers and also the hybridization the it identify are provided as follows.

2: sp hybridization

3: sp2 hybridization

4: sp3 hybridization

5: hybridization

The formula to discover the number is offered by,

Hybridization Number = valence electron number + monovalent + (negative charge) – (positive charge)/2

The iodine atoms" valence electrons will be 7 because there space 7 electrons in the outermost shell. The variety of the monovalent atom is 2 since the two out of three iodines are monovalent. Now, comes to the charge of the I3- ion, it has actually a an unfavorable charge. So, this an adverse charge worth will be 1.

Now if we ar all the worths according to the formula, the becomes,




Thus, the hybridization number is 5, which means it is sp3d hybridized.

Another method to find the hybridization that a given molecule is by acquisition the aid of lone pairs and valence electrons. Here, the number of lone pairs in the molecule is 3 and the number of atoms share valence electrons is 2.

Henceforth, 3+2=5, which likewise determines the exact same sp3d hybridization.

Name of the Molecule

Triiodide Ion

Molecular Formula


Hybridization Type


Bond Angle




Lewis Structure

Lewis framework is nothing but the electron depiction of the molecules. There room lone pairs and valence electrons that help in identify the shape and also hybridization that the molecule. Together there room Iodine molecules, one molecule that iodine will current in the centre. Iodine likewise lies in the seventh team of the routine table and has 7 valence electron in its external orbit.

Here, we have actually 3 molecule of iodine, which together with an extra electron that gives it a an adverse charge. So, the complete valence electrons count is given by 7×3 + 1= 22.

Moreover, in this molecule, there room 22 valence electron in total. Now, there is an octet dominion followed by every atom. According to this rule, every atom should have actually 8 electrons in their outer orbit. So, if there room 8 electrons in the main atom"s outer shell, over there exist 2 various other atoms compelled to complete their octet. As all the atoms require 8 electron in their external shell because that octet completion, 1 central iodine"s electron atom will certainly be taken by both adjoining iodine atoms. It method 8-1-1=6 because both the atoms will certainly take the electrons.

So, the valence electron on the central atom that iodine will end up being 6. This 6 electron will form the electron lone pairs that carry out not bond. Together it forms the pair of electrons now, there will be 3 lone pairs, and 2 bond bag of the electrons because each Iodine atom has a bond through the main atom sharing 1 electron each. So, in total, there are 3 lone pairs and also 2 bond bag on the main atom.

I3 molecular Geometry and Bond Angles

The molecular geometry of I3- is linear. If there space 3 Iodine atoms, among the atoms has actually a an adverse charge, which additional gives 2 shortcut pairs and also 3 lone bag of electrons. That is steric number will certainly be 5. The 3 lone pairs will certainly repel each other and also take up the equatorial positions. The staying 2 Iodine atoms existing at 180° from every other.

Polarity that I3- Ion

So, there is a tricky part of this ion here. Firstly, we can call the charge existing on it as a polyatomic ion instead of a molecule. Ions are the charges the we watch on the molecules. Together I3- has actually only 1 electron, this Ion has an overall an unfavorable charge. Whereas, the molecules have polarity because it has actually both the charges which are charged partly positively and negatively. Over there exists a dipole moment on the molecules based top top the fees separation on the molecule. If the distance between both charges is large, then the dipole moment will additionally become larger.

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However, when we talk about II3- ion, that is a negatively charged ion. Also while drawing its Lewis structure, we execute not see any kind of dipole minute of the polar bond in it, due to the fact that the overall charge itself is an adverse on the ion. So, it is no polar nor nonpolar. However, if we have to describe the ion, we can use the expression "like a polar molecule" because I3- is soluble in water.