Lewis Structure For Thiocyanate Ion

Lewis Structure and Resonance Structures of SCN^- (Thiocyanate ion)

Lewis structure and resonance structures of thiocyanate ion is drawn step past stride in this tutorial. Total valence electrons of atoms, negative charge are considered to draw the SCN- lewis structure. Thiocyanate ion includes iii kinds atoms.

written by: Heshan Nipuna, terminal update: 29/05/2020

Lewis Structure of thiocyanate ion

lewis structure of SCN-

Now, we are going to larn, how to draw this lewis construction of ClO_three ^- ion pace by stride.

Steps of cartoon SCN^- lewis structure

Following steps are required to draw SCN^- lewis structure and they are explained in detail in this tutorial.

Find total number of electrons of the valance shells of sulfur, nitrogen and carbon atoms and including charge of the -one charge
Total electrons pairs in valence shells
Determine middle cantlet from carbon, nitrogen and sulfur atoms
Put lonely pairs on atoms and mark charges on atoms
Stability of lewis structure - Bank check the stability and minimize charges on atoms by converting alone pairs to bonds to obtain the best lewis structure.

Cartoon right lewis structure is important to draw resonance structures of SCN^- ion.

Total number of electrons of the valance shells of carbon, nitrogen and sulfur atoms and charge of the anion

In that location are three types of atoms; carbon, nitrogen and sulfur. These atoms are located at different groups.
Carbon is located at group 4 and has four electrons in its valence shell. Nitrogen is at group five and contains v electrons in its valence shell. Other cantlet, sulfur is a group 16 element and has half-dozen electrons in its valence shell.

Total valence electrons given by carbon cantlet = 4*1 = four
Total valence electrons given by nitrogen atom = 5*1 = 5
Full valence electrons given by sulfur cantlet = vi*1 = 6

Due to -one charge, another electrons is added to the total valence electrons count.

Due to -i accuse, received electrons to valence electrons= 1

Full valence electrons = four + v + 6 + one = xvi

Full valence electrons pairs

Full valance electrons pairs = σ bonds + π bonds + solitary pairs at valence shells

Total electron pairs are adamant past dividing the number full valence electrons by two. For, SCN^- ion, at that place are 16 valence electrons, so total pairs of electrons are 8.

Center atom of SCN^- ion

For being the center atom, ability of having greater valance is a reason. If we consider each element, maximum valence of carbon, nitrogen and sulfur are 4, five and vi respectively. You may know, in then many compounds which are include carbon has four bonds around carbon atom. Yet, for SCN^- ion, sketch is every bit below.

Sketch of SCN^- ion

sketch of SCN- ion

Alone pairs on atoms

There are only two (2) bonds around middle atom in the sketch of thiocyanate ion; carbon (C-O and C-Southward). Therefore, at present six (8-2) electrons pairs are remaining to mark lone pairs.
As the next pace, mark those 6 valence electrons pairs on outside atoms (nitrogen and sulfur atoms) as solitary pairs. Each outside atom will have three lone pairs. Therefore, total of vi electrons pairs are marked on nitrogen and sulfur atoms. Now, there is more electrons pairs to mark on carbon atom.

mark lone pairs on sulfur and nitrogen atoms in thiocynate lewis structure

Bank check the stability of drawn structure of SCN^- ion and reduce charges on atoms past converting lone pairs to bonds

Bank check charges on atoms and mark them as beneath. Lowering the charges on atoms is important to obtain the best lewis structure of the ion.

Mark charges on atoms

mark charges on atoms as a step of SCN- lewis structure.jpg

There are charges on every atoms of higher up structure. Therfore, drawn construction for SCN^- is non a stable structure. Also, when accuse of an atom is great (like +2, +3), that structure go more than unstable. When a molecule or ion has and then many charges on atoms and charge is great that construction is not stable.

Now, nosotros should effort to minimize charges past converting lone pair or pairs of outside atoms to bonds. So nosotros convert i lonely pair of nitrogen atom as a C-N bond as in the post-obit figure.

minimize charges of atoms in thiocyanate ion

Now there is a double bail betwixt carbon atom and nitrogen cantlet. And charge of carbon atom is reduced from +2 to +ane and for nitrogen, charge is reduced to -ane. Still sulfur has a -1 charge.

Only, there are still charges on all atoms. If possible, nosotros should reduce charges furthermore. Therefore, a lone pair of sulfur atom is transferred every bit a South-O bail (See the effigy).

minimize charges to get best lewis structure of SCN-

Now, there are no charges around carbon atom and sulfur atom. Only nitrogen has a -1 charge. That is an acceptable bespeak because nitrogen is the most electronegative element from these three elements. Therefore, this new structure is the best lewis structure of thiocyanate ion.

Questions

What are the deviations of SCN^- lewis construction from usual steps of drawing a lewis structure?

In SCN^- ion, carbon atom is the center atom. Usually we think, heart cantlet should be an element which has a college valence. In SCN^-, nitrogen has highest valeence. But, nitrogen is not the center atom of SCN^- ion. That is a deviation from usual do of drawing a lewis structure.