SCN- Lewis Structure & Characteristics: 13 Complete Facts


The valence electrons of molecules represented by lines (single bonds) and dots (electrons) are known as lewis structures. Let us discuss SCN- lewis’s structure.

SCN- lewis structure contains 1 S atom, 1 C atom, and 1 N atom. It is a triatomic anion. It has one negative charge due to gain of electrons. The carbon atom is a central atom as it is least electronegative than sulfur and nitrogen atoms. SCN- with double bonds is a more stable structure.

SCN- (thiocyanate ion) has single bonds within S and C atoms (S-C) and also within C and N atoms (C-N) shown with a line. Extra unshared electrons get placed on bonded outer S and N atoms. Let us discuss the lone pairs, bond angle hybridization, shape, and some more characteristics of SCN- lewis structure.

How to draw SCN- lewis’s structure?

Look upon the following detailed steps to draw the SCN- lewis structure.

Valence electrons and bonding:

Do the summation of all valence electrons available on each S, C, and N atom of SCN- lewis structure to know the total valence electrons on it. Make single bonds within all three S, C, and N atoms shown with lines.

Lone pair electrons and Octet rule:

Extra valence unshared electrons are put on bonded sulfur and nitrogen atoms as lone pair electrons and counted them. Later apply the octet rule on each S, C, and N atom to note its octet that they have complete or incomplete octets.

Formal charge and shape of SCN-:

Calculate the formal charge formed on SCN- lewis structure with the help of the given formula. Later recognize the hybridization, shape, and bond angle of SCN- ion.

SCN- lewis structure

SCN- valence electrons

The electrons present on the outermost orbital or shell of any element/molecule is known as valence electrons. Below see some brief discussions on SCN- valence electrons.

SCN- lewis structure contains 16 overall valence electrons. The S atom has 6 valence electrons as it is from the 16th group. The C atom has 4 valence electrons as it comes from the 14th group of the periodic table. The N atom has 5 valence electrons due to their 15th group of the periodic table.

The calculation for SCN- lewis structure valence electrons is given below.

  • Sum of S, C and N atoms valence electrons = 6 + 4 + 5 = 15
  • Addition of 1 electron due to -1 charge on SCN- = 15 + 1 = 16
  • SCN- has total of 16 valence electrons.
  • To know total electron pairs on SCN- divide valence electrons by 2 = 16 / 2 = 8
  • Thus, SCN- lewis structure has total of 16 valence electrons and 8 electron pairs.

SCN- lewis structure lone pairs

Extra remaining unshared or non–bonding electrons present in the molecule is known as lone pair electrons. Here is some discussion on SCN- lewis structure is given below.

SCN- lewis structure contains 6 lone pair electrons. It has a total of 16 valence electrons. Out of which 4 valence electrons are being bond pair electrons as it forms 2 covalent S – C and C – N bonds. The remaining extra 12 unshared valence electrons are placed over the outer bonded S and N atoms.

All the 12 unshared valence electrons get put on S and N atoms. Each S and N atoms have 6 non – bonding electrons. Thus these 6 non – bonding electrons get paired and become 3 lone pair electrons. Therefore, each S and N atom contains 3 lone pairs and it has a total of 6 lone pair electrons.

SCN- lewis structure octet rule

The presence of 8 electrons in the outer shell of atoms, so it has a complete or incomplete octet described octet rule. Let us discuss SCN- octet rule.

SCN- lewis structure shows complete octets of both outer S and N atoms. Rather the central C atom has an incomplete octet. The Central C atom contains only 4 bonding electrons forming two S – C and C – N bonds. As the carbon atom does not contain 8 electrons it has an incomplete octet.

Sulfur and nitrogen atoms contain 6 non – bonding electrons and 2 bonding electrons. Thus both bonding S and N atoms engaged 8 electrons ( 6 N.B.E + 2 B.E = 8 E. ) around it and had complete octets.

SCN- lewis structure formal charge

The stability of a molecule determines by its positive or negative formal charge present in it. Let us discuss the brief calculative part of SCN- lewis structure below.

The formal charge of SCN- lewis structure is = (valence electrons – non-bonding electrons – ½ bonding electrons)

The explanation of the calculation of SCN- lewis structure formal charge is shown below the table.

Atoms of SCN- lewis structureValence electrons on S, C and NNon – bonding electrons on S, C, and NBonding electrons on S, C, and NThe formal charge on S, C, and N
Sulfur (S) atom060602( 6 – 6 – 2 / 2 ) = – 1
Carbon (C) atom040004( 4 – 0 – 4 / 2 ) = + 2
Nitrogen (N) atom050602( 5 – 6 –  2 / 2 ) = – 2
The formal charge of SCN- ion, S = – 1, C = + 2, N = – 2

SCN- lewis structure resonance

The two or more forms of structures formed due to the movement of electrons in the same molecule are resonance structures. Let us discuss briefly SCN- resonance structure.

SCN- lewis structure has 2 resonance structures. Electrons get moved within SCN- to form multiple bonds. So the formal charge on SCN- ion is reduced to form a stable lewis structure. The second resonance structure is the most stable as the -1 charge is present on a more electronegative N atom.

The SCN- resonating structures are described in the below table.

Resonance structuresFormal chargesBondingStabilityMovement of electrons
Lewis StructureS = – 1, C = + 2, N = – 2S – C (single bond), C – N (single bond)  Not stableNo electron movement
Resonance Structure 1S = – 1, C = 0, N = 0S – C (single bond), C ≡ N (triple bond)Not stable2 electrons pairs moved from N to form a triple bond
Resonance Structure 2S = 0, C = 0, N = – 1S = C (double bond), C = N (double bond)Stable1 – 1 electrons pair moved from S and N to form double bonds
Resonance structures of SCN- ion
Two resonance structures of SCN- ion

SCN- lewis structure shape

Atomic arrangement with its angle and bonding in any molecule determines its molecular shape. Here we are discussing below on SCN- shape.

SCN- lewis structure has a linear shape. It contains 1 central C atom and bonded two atoms i.e. S and N atoms. The Central C atom does not have lone pair electrons, thus there is no repulsion within the molecule. Hence as per VSEPR theory, it has an AX2 generic formula and linear geometry and shape.

SCN- hybridization

The overlapping or mixing of atomic orbitals to form new hybrid orbitals having equal energy is known as hybridization. Below is a brief discussion on SCN- hybridization.

SCN- lewis structure has sp hybridized central carbon atom. The central carbon atom of SCN- ion has steric number 2. It is calculated as Steric number = bonding atoms to C atom + lone pairs on C atom. Hence, steric number of C on SCN- is 2 + 0 = 2.

The VSEPR theory says the molecule with 2 steric numbers has ‘sp’ hybridization. Thus in SCN- ion, it has mixing and recasting of 1’s’ and 1’p’ orbital of a carbon atom and forms new ‘sp’ hybrid orbitals of the same energy.

SCN- bond angle

The angle within two immediate bonds within the molecules is called bond angles. Take a brief look at SCN- ion bond angle below.

SCN- lewis structure has an 1800 bond angle. SCN- is a triatomic ion consisting of three atoms linearly. All S, C, and N atoms lie in the same plane. There is no lone pair on the central C atom and no repulsion. So, all the atoms are in straight lines forms a linear shape, and have an S-C-N 1800 angle.

Is SCN- polar or nonpolar?

Polarity depends on the electronegativity, equal – unequal electron sharing, net or zero dipoles on molecules, etc. Let us see below the polarity of SCN- lewis structure.

SCN- lewis structure is a polar molecule. It has a big electronegativity difference between all S, C, and N atoms. Central C and outer S atoms have 0.03 and C and N atoms have 0.49 electronegativity difference value. Due to this much electronegativity difference, it has a net dipole moment.

Why and how SCN- is polar?

SCN- is a polar anion because it has a more electronegative N atom which attracts electron cloud to itself. Also, it has a triple bond between C and N atoms, so there is no equal sharing of electrons. Due to this, dipoles get created within the molecule.

Thus, partial positive charge develops on C and partial negative charge develops on N atom of SCN- ion. Also, it has an asymmetric arrangement of atoms due to its linear shape and presence of two different bonding atoms with unequal electron distribution.

Is SCN- ionic or covalent?

Covalent compounds are those which consist of covalent bonds with other small molecular groups present in them. Let us see below that SCN- is an ionic or covalent ion.

SCN- is ionic in nature and not covalent. Because SCN- is an anion having -1 negative formal charge present on it. The stable form of SCN- ion does not contain single covalent bonds as it has two S=C and C=N double bonds. It is a conjugate base formed from HSCN (thiocyanic acid).

Why and how SCN- is ionic?

SCN- ion is an anion because it has the ability to accept an electron. The sum valence electrons of S, C, and N atoms are basically 15 but 1 electron is added to it. This generates a negative charge on the SCN molecule making it an anion. Hence it shows its ionic nature.

Is SCN- a polydentate ligand?

Polydentate ligands are ligands that contain two or more two donor atoms in their molecule. Here we are discussing whether is SCN- a polydentate ligand or not.

SCN– is an ambidentate ligand and not polydentate. Because it has two different donor sites S and N atoms. It can donate its electrons to the central metal atom in complexes either by S or by N only at one time. It cannot form coordinate bonds with a central metal atom at the same time.

Conclusion:

SCN- lewis structure contains 16 valence electrons and 6 lone pair electrons. It has a formal charge of -1 on S, +2 on C, and -2 on N atoms. It has complete octets of S and N atoms while the central C atom has an incomplete octet. It is linear in shape, ‘sp’ hybridized with 1800 bond angle. It is an ionic molecule, polar in nature, and an ambidentate ligand.

Dr. Shruti Ramteke

Hello everyone I am Dr. Shruti M Ramteke, i did my Ph.D in chemistry. I have five years of teaching experience for 11-12 standard, B,Sc and MSc in chemistry subject. I have published total five research articles during Ph.D on my research work and i have fellowship from UGC for my Ph.D. My Masters with specilization Inorganic chemistry and my graduation with chemistry, zoology and environmental science subjects. thank You

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