SeO42- Lewis structure

SeO₄^2- (selenate) has one selenium atom and four oxygen atoms.

In SeO₄^2- Lewis structure, there are two double bonds and two single bonds around the selenium atom, with four oxygen atoms attached to it. The oxygen atom with double bonds has two lone pairs, and the oxygen atom with single bonds has three lone pairs.

Also, there is a negative (-1) charge on the oxygen atom with single bonds.

Alternative method: Lewis structure of SeO₄^2-

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, both selenium and oxygen lie in group 16.

Hence, both selenium and oxygen have six valence electrons.

Since SeO₄^2- has one selenium atom and four oxygen atoms, so…

Valence electrons of one selenium atom = 6 × 1 = 6
Valence electrons of four oxygen atoms = 6 × 4 = 24

Now the SeO₄^2- has a negative (-2) charge, so we have to add two more electrons.

So the total valence electrons = 6 + 24 + 2 = 32

Learn how to find: Selenium valence electrons and Oxygen valence electrons

• Second, find the total electron pairs

We have a total of 32 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 = 32 ÷ 2 = 16

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 16 electron pairs. And four Se — O bonds are already marked. So we have to only mark the remaining twelve 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 oxygen is a period 2 element, so it can not keep more than 8 electrons in its last shell.

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

So for each oxygen, there are three lone pairs, and for selenium, there is zero lone pair because all twelve electron pairs are over.

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 – 0 – ½ (8) = +2

For each oxygen atom, formal charge = 6 – 6 – ½ (2) = -1

Here, both selenium and oxygen atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both selenium and oxygen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

Convert a lone pair of the oxygen atom to make a new Se — O bond with the selenium atom as follows:

Since there are charges on selenium and oxygen atoms, again convert a lone pair of the oxygen atom to make a new Se — O bond with the selenium atom as follows:

Final structure

The final structure of SeO₄^2- consists of a central selenium atom linked to four oxygen atoms. In this configuration, the selenium atom utilizes an expanded valence shell to form two double covalent bonds and two single covalent bonds, leaving no lone pairs on the selenium. Within this layout, each of the four oxygen atoms satisfies the octet rule: the two double-bonded oxygen atoms maintain two lone pairs each, while the two single-bonded oxygen atoms retain three lone pairs each. This arrangement represents the most stable state for the ion because it minimizes formal charges across the structure, placing the negative formal charges on the oxygen atoms, which possess a higher electronegativity than selenium. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the selenate ion.

To properly represent this as a polyatomic ion, the entire Lewis structure is enclosed within square brackets. The overall charge of 2- is then written as a superscript outside the brackets at the top right, indicating that the structure possesses two additional electrons beyond the valence count of the neutral atoms.

Next: BrCl₄^– Lewis structure

External video

• How to Draw the Lewis Dot Structure for SeO4 2- : Selenate ion – YouTube • Wayne Breslyn

External links

• https://homework.study.com/explanation/draw-the-lewis-structure-for-seo42.html
• https://www.chegg.com/homework-help/questions-and-answers/choose-best-lewis-structure-seo42–q1725231
• https://www.numerade.com/ask/question/part-a-draw-a-lewis-diagram-for-seo42-in-which-all-atoms-have-a-formal-charge-of-zero-part-b-draw-a-lewis-structure-for-seo42-in-which-the-octet-rule-is-satisfied-on-all-atoms-and-show-all-n-96122/
• https://geometryofmolecules.com/so42-lewis-structure-hybridization-bond-angle-and-molecular-geometry/
• https://oneclass.com/homework-help/chemistry/7032595-seo4-2-lewis-structure.en.html
• https://www.answers.com/chemistry/What_is_the_shape_of_SeO42