SeI2 Lewis structure

SeI₂ has one selenium atom and two iodine atoms.

In SeI₂ Lewis structure, there are two single bonds around the selenium atom, with two iodine atoms attached to it. Each iodine atom has three lone pairs, and the selenium atom has two lone pairs.

Alternative method: Lewis structure of SeI₂

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, selenium lies in group 16, and iodine lies in group 17.

Hence, selenium has six valence electrons and iodine has seven valence electrons.

Since SeI₂ has one selenium atom and two iodine atoms, so…

Valence electrons of one selenium atom = 6 × 1 = 6
Valence electrons of two iodine atoms = 7 × 2 = 14

And the total valence electrons = 6 + 14 = 20

Learn how to find: Selenium valence electrons

• Second, find the total electron pairs

We have a total of 20 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 20 ÷ 2 = 10

• Third, determine the central atom

We have to place the least electronegative atom at the center.

Since selenium is less electronegative than iodine, assume that the central atom is selenium.

Therefore, place selenium in the center and iodines on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 10 electron pairs. And two Se — I bonds are already marked. So we have to only mark the remaining eight electron pairs as lone pairs on the sketch.

Also remember that selenium is a period 4 element, so it can keep more than 8 electrons in its last shell. And iodine is a period 5 element, so it can keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are iodines.

So for each iodine, there are three lone pairs, and for selenium, there are two lone pairs.

Mark the lone pairs on the sketch as follows:

Formal charge

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For selenium atom, formal charge = 6 – 4 – ½ (4) = 0

For each iodine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, both selenium and iodine atoms do not have charges, so no need to mark the charges.

Final structure

The final structure of SeI₂ features a central selenium atom connected to two iodine atoms through single covalent bonds. In this arrangement, the selenium atom satisfies the octet rule by forming two bonding pairs and retaining two lone pairs. Each iodine atom also fulfills its octet by maintaining three lone pairs of its own alongside the single shared bond. This setup is the most stable because it results in formal charges of zero for all atoms, representing the most energetically favorable state for the molecule. Consequently, this specific electronic distribution serves as the definitive and most accurate Lewis representation of this molecule.

Next: H₂Te Lewis structure

External links

• https://www.bartleby.com/questions-and-answers/draw-a-lewis-structure-for-sei2-draw-a-lewis-structure-for-sih2se-draw-a-lewis-structure-for-ps2-not/61043cda-a798-41dc-a4d9-5aa404d0fac4
• https://www.chegg.com/homework-help/questions-and-answers/draw-lewis-structure-sei2-include-electron-pair-geometry-hybridization-sigma-bonds-pi-bond-q88180473