CSe2 Lewis structure

CSe₂ (carbon diselenide) has one carbon atom and two selenium atoms.

In the CSe₂ Lewis structure, there are two double bonds around the carbon atom, with two selenium atoms attached to it, and on each selenium atom, there are two lone pairs.

Alternative method: Lewis structure of CSe₂

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, carbon lies in group 14, and selenium lies in group 16.

Hence, carbon has four valence electrons and selenium has six valence electrons.

Since CSe₂ has one carbon atom and two selenium atoms, so…

Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of two selenium atoms = 6 × 2 = 12

And the total valence electrons = 4 + 12 = 16

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

• Second, find the total electron pairs

We have a total of 16 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 = 16 ÷ 2 = 8

• Third, determine the central atom

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

Since carbon and selenium have the same electronegativity value, we can assume any one as the central atom, right?

But if we place selenium in the center and carbon outside, and calculate the formal charge, then we do not get the formal charges on atoms closer to zero.

And the structure with the formal charges on atoms closer to zero is the best Lewis structure.

Hence, here we have to assume that the central atom is carbon.

Therefore, place carbon in the center and seleniums on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 8 electron pairs. And two C — Se bonds are already marked. So we have to only mark the remaining six electron pairs as lone pairs on the sketch.

Also remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell. And selenium is a period 3 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 seleniums.

So for each selenium, there are three lone pairs, and for carbon, there is zero lone pair because all six 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 carbon atom, formal charge = 4 – 0 – ½ (4) = +2

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

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

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

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

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

Final structure

The final structure of CSe₂ comprises a central carbon atom linked to two selenium atoms via double covalent bonds. Within this configuration, the carbon atom successfully completes its octet by sharing all four of its valence electrons, while each selenium atom also satisfies the octet rule by retaining two lone pairs. This specific arrangement results in formal charges of zero for every atom involved, representing the most energetically favorable and stable electron distribution. Consequently, this linear bonding pattern serves as the definitive and most accurate Lewis representation of carbon diselenide.

Next: AlBr₃ Lewis structure

External links

• https://techiescientist.com/cse2-lewis-structure/