OCN- Lewis structure

OCN^– (cyanate) has one oxygen atom, one carbon atom, and one nitrogen atom.

In the OCN^– Lewis structure, there is a single bond between carbon and oxygen atom, and a triple bond between carbon and nitrogen atom. The oxygen atom has three lone pairs, and the nitrogen atom has one lone pair.

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

Alternative method: Lewis structure of OCN^–

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, oxygen lies in group 16, carbon lies in group 14, and nitrogen lies in group 15.

Hence, oxygen has six valence electrons, carbon has four valence electrons, and nitrogen has five valence electrons.

Since OCN^– has one oxygen atom, one carbon atom, and one nitrogen atom, so…

Valence electrons of one oxygen atom = 6 × 1 = 6
Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of one nitrogen atom = 5 × 1 = 5

Now the OCN^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 6 + 4 + 5 + 1 = 16

Learn how to find: Oxygen valence electrons, Carbon valence electrons, and Nitrogen 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 is less electronegative than oxygen and nitrogen, assume that the central atom is carbon.

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

• And finally, draw the rough sketch

Lone pair

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

Also remember that all three (oxygen, carbon, and nitrogen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are oxygen and nitrogen.

So for oxygen and nitrogen, 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 oxygen atom, formal charge = 6 – 6 – ½ (2) = -1

For carbon atom, formal charge = 4 – 0 – ½ (4) = +2

For nitrogen atom, formal charge = 5 – 6 – ½ (2) = -2

Here, all three atoms have charges, so mark them on the sketch as follows:

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

Here we have to convert a lone pair of the nitrogen atom (instead of the oxygen atom). Because nitrogen is less electronegative than oxygen. And so, it can give more valence electrons to share them.

Or remember this way, in OCN^– and similar type structures, we have to make sure that the negative charge comes on the most electronegative element. In this case, the most electronegative element is oxygen.

Therefore, convert a lone pair of the nitrogen atom to make a new C — N bond with the carbon atom as follows:

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

Final structure

The final structure of OCN^– comprises a central carbon atom linked to an oxygen atom and a nitrogen atom. In this configuration, the carbon atom forms a triple bond with the nitrogen atom and a single covalent bond with the oxygen atom to fulfill the octet rule. Within this layout, the nitrogen atom satisfies its octet by maintaining one lone pair alongside the triple bond, while the oxygen atom fulfills its octet by retaining three lone pairs. This arrangement represents the most stable state for the ion because it results in a formal charge of 0 on the carbon, 0 on the nitrogen, and -1 on the oxygen, which is the most electronegative atom in the species. Consequently, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the cyanate ion.

To properly represent this as a polyatomic ion, the entire Lewis structure is enclosed within square brackets. The overall charge of 1- is then written as a superscript outside the brackets at the top right, indicating that the structure possesses one additional electron beyond the valence count of the neutral atoms.

Next: ICl₄^– Lewis structure

External video

• OCN- Lewis Structure: How to Draw the Lewis Structure for OCN- – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/ocn-lewis-structure/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/OCN–lewis-structure.html
• https://socratic.org/questions/what-is-the-lewis-structure-for-ocn
• https://topblogtenz.com/ocn-lewis-structure-molecular-geometry-hybridization-polar-or-nonpolar/
• https://techiescientist.com/nco-lewis-structure/