# Lewis Dot Structures of the Cyanamide ion NCN^{-2}

A simple procedure for writing ** Lewis Dot Structures** was given in a previous post entitled “**Lewis Structures and the Octet Rule**”. Several worked examples relevant to this procedure were given in previous posts please see the **Sitemap - Table of Contents (Lewis Electron Dot Structures)**.

Let us consider the case of the **NCN ^{-2} ion **and draw the

**Lewis dot structures**:

__Step 1__: Connect the atoms with single bonds.

__Step 2__: Calculate the # of electrons in ð bonds (**multiple bonds**) using ** formula (1)**:

Where n in this case is 3 since **NCN ^{-2}**consists of 3 atoms.

Where V = 5 + 4 + 5 – (-2) = 16

Therefore, P = 6n + 2 – V = 6 *3 + 2 – 16 = 4 **Therefore, there are either 2 double bonds or 1 triple bond.**

__Step 3 & 4__: The **Lewis structures of** of** NCN ^{-2}** are

**as follows:**

The ion represented by the **electron dot structure** #1 is the most stable comparing to the #2 and #3 because of less charge separation. The cyanamide ion is isoelectronic and hence isostructural with the CO_{2} molecule.

__Relevant Posts__

Lewis Structures|Octet Rule: A Simple Method to write Lewis Structures

Canonical Structures - Lewis Dot Structure of OCN-

__References__

- G.N. Lewis, J.A.C.S, 38, 762-785, (1916)
- E. C. McGoran, J. Chem. Educ., 68, 19-23 (1991)
- A.B.P. Lever, J. Chem. Educ., 49, 819-821, (1972)

__Key Terms__

** resonance structures of cyanate ion NCN-2**,

__Lewis electron structures of cyanamide ion,__**,**

__chemical formula of the cyanamide__**,**

__simple procedure for drawing Lewis structures of cyanamide ion__

I'm confused, I thought there would be 18 electrons not 16, there is a negative charge of 2, thus there are 2 extra electrons? In which case there would be a single bond and a double bond, along with a lone pair. No?

ReplyDelete