CNO- lewis structure, Characteristics: 13 Facts You Should Know


CNO- is the chemical formula for Fulminate ion. The CNO- ion is resembles with OCN- ion but both ions have complete different properties.

Fulminate ion (CNO-) is an anion consists of three elements i.e. one carbon, one nitrogen and one oxygen. It is also known as carbidooxidonitrate(1-). It is a form of pseudohalide anion. It acts as a conjugate base of an isofulminic acid and fulminic acid. Here we are discussing on CNO- lewis structure and characteristics.

How to draw CNO- lewis structure?

To draw the lewis structure there are some rules or steps to remember and follow. The following are the some steps to draw CNO- lewis structure.

Step – 1 Note the group position of C, N and O atoms for counting of total valence electrons present on CNO- ion or lewis structure.

Step – 2 Selection of central atom which is least electronegative in nature. Electronegativity of C is 2.55, N is 3.04 and O is 3.44. Hence carbon atom is least electronegative than N and O atom. Thus, C atom occupies the central position in CNO- lewis structure.

Step – 3 Now make a possible bonding between C and N and C and O atoms.

Step – 4 In bonding some valence electrons get engaged and being bond pairs. So the left over valence electrons get shared within outer N and O atoms.

Step – 5 Check whether the C, N and O atom have complete octet after final distribution of electrons.

Step – 6 Lone electron pairs count on CNO- ion.

Step – 7 Calculate the formal charge present on CNO- lewis structure.

Step – 8 Finally determine its shape and geometry, also hybridization and bond angle.

CNO- valence electrons

The CNO- lewis structure includes only three elements i.e. one carbon, one nitrogen and one oxygen atom. Carbon atom lies in the 14th group under periodic table, nitrogen atom lies in the 15th group under periodic table and oxygen atom lies under 16th group under periodic table. Thus, the C, N and O atoms has 4, 5 and 6 valence electrons present in its outermost valence shell orbital.

Carbon atom of CNO- ion have valence electrons is = 04 x1 = 4 (C)

Nitrogen atom of CNO- ion have valence electrons = 05 x 1 = 5 (N)

Oxygen atom of CNO- ion have valence electrons = 06 x 1 = 6 (O)

Also we have to add extra one electron for the minus or negative (-) charge having on CNO- ion.

Thus, total valence electrons available on CNO- lewis structure = 04 (C) + 05 (N) + 06 (O) + 01 (-) = 16

Hence, total sixteen valence electrons are present in CNO- lewis structure.

If we want to know total electron pair available on CNO- lewis structure, then divide the total valence electrons of CNO- ion by two.

Therefore, total electron pair on CNO- ion = 16 / 2 = 8

So, there are total eight electron pairs present on CNO- ion.

Valence electrons present in CNO- lewis structure

CNO- lewis structure octet rule

In CNO- lewis structure, there are total 16 valence electrons are present. If there is the formation single covalent bond within C and N (C-N) and N and O (N-O), four electrons are being bond pair electrons, as two electrons are present in single bond.

So, C and O atom have eight electrons, thus they both have complete octet. But the central nitrogen atom has only four electrons thus it has incomplete octet. This kind of structure is unstable as it has only two single bonds present in it and the central N atom have incomplete octet.

Also the formal charge on this kind of structure is much more due to which it becomes unstable. So, we have to move two electron pairs from carbon atom to form triple bond within carbon and nitrogen atoms. By forming the triple bond between carbon and nitrogen atom all the atoms i.e. C, N and O have complete octet.

Means they have possess eight electrons in it and also the formal charge on it get minimize. Thus this structure is a stable form of CNO- structure.

Octet rule on CNO- lewis structure

CNO- lewis structure lone pairs

In CNO- lewis structure, it has 16 total valence electrons out of them four electrons are converted to bond pairs as they form two single covalent bonds between C and N (C-N) and N and O (N-O) atoms.

Thus we have remained only 12 valence electrons for more sharing within outer C and O atoms. All this 12 electrons get placed on C and O atom.Now, the outer carbon and oxygen atom can get more six – six electrons. Thus the carbon atom now has six non – bonding electrons and the oxygen atom has now six non – bonding electrons present on it.

Thus, these non – bonding electrons get paired up as a pair of two electrons, so each C and O atom has three lone electron pairs each. Therefore, the carbon atom has three lone pair electron and O atom has three lone pair electron. Hence there are total six lone electron pair is present on CNO- lewis structure.

CNO- lewis structure formal charge

The lewis structure is more stable if the minimum formal charge is present on the atoms of its molecule. The formal charge counting or calculation is done with a given formula shown as below.

Formal charge = (valence electrons – non-bonding electrons – ½ bonding electrons)

To calculate the formal charge present on CNO- lewis structure we have to count the formal charge present on all the atoms present in it. Thus we have to calculate the formal charge of Carbon, nitrogen and oxygen atoms separately.

Carbon atom: Carbon atom has Valence electrons = 04

                       Carbon atom has Non-bonding electrons = 06

                       Carbon atom has Bonding electrons =02

Formal charge on carbon atom of CNO- ion is = (4 – 6 – 2/2) = -3

Thus, formal charge present on carbon atom is minus three (-3).

Nitrogen atom:Nitrogen atom has Valence electron = 05

                        Nitrogen atom has Non-bonding electron = 00

                        Nitrogen atom has Bonding electrons =04

Formal charge on nitrogen atom of CNO- ion is = (05 – 00 – 4/2) = +3

Thus, formal charge present on nitrogen atom is plus three (+3).

Oxygen atom: Oxygen atom has valence electrons = 06

                       Oxygen atom has non-bonding electrons = 06

                       Oxygen atom has bonding electrons = 02

Formal charge on oxygen atom of CNO- ion is = (6 – 6 – 2/2) = -1

Thus, formal charge present on oxygen atom is minus one (-1)

Therefore, the complete formal charge present on C, N and O atoms of CNO- lewis structure is -3, +3 and -1 respectively.

Formal charge on CNO- lewis structure

CNO- lewis structure resonance

The CNO- ion shows three types of resonance structure. Initially the CNO- lewis structure has single covalent bonds between C and N (C-N) and N and O (N-O) atoms. Also there are three – three lone electron pairs are present on C and O atom. The highest formal charge is present in this initial structure i.e. c has -3, N has +3 and O has -1.

In first resonance structure, there is two electron pair moved from C atom to form a triple bond with C and N atom rather a single bond is present within N and O atoms. The formal charge get minimize and form a stable form of resonance structure of CNO- ion. It has -1, +1 and -1 formal charge present on C, N and O atoms of CNO- ion.

In second structure, one electron pair get moved from both C and O atoms to form carbon nitrogen (C=N) double bond and nitrogen oxygen (N=O) double bond. This resonance structure also has more formal charge as compared to first resonance structure i.e. C atom has -2, N atom has +1 and O atom has zero formal charge present on it.

Tin third resonance structure, two electron pairs get moved to form triple bond between N and O atoms. This structure also has more formal charge as compared to first two resonance structure. C has -3, N has +1 and O has +1 formal charge present on it. Thus second and third resonance structures are unstable.

Resonance structures of CNO- lewis structure

CNO- lewis structure shape

According to VSEPR theory module for geometry and shapes of molecules, the molecule containing three atoms i.e. one central atom and two bonded atoms with no lone electron pair present on central atom is comes under the AX2 generic formula. Where, A = central atom and E = bonded atoms. Thus this kind of molecules has linear molecular shape and electron geometry.

The CNO- lewis structure also consists of three atoms one nitrogen central atom and two bonded atoms i.e. carbon and oxygen. There is no lone electron pair present on central nitrogen atom, thus the CNO- lewis structure follows AX2 generic formula of VSEPR theory. Hence, CNO- lewis structure has linear molecular shape and electron geometry.

CNO- hybridization

The CNO- lewis structure has AX2 generic formula , thus it has linear molecular geometry and electron geometry. As the CNO- ion has three elements i.e. central nitrogen atom and bonded C and O atoms with no lone pair on central N atom. So, they do come under AX2 generic formula by which it has sp hybridization. Thus the CNO- lewis structure has sp hybridization as per the VSEPR theory.

CNO- lewis structure angle

The CNO- lewis structure has linear molecular shape and electron geometry and also it has sp hybridization as it follows AX2 generic formula. Thus, it has 180 degree bond angle between carbon and nitrogen (C-N) and nitrogen and oxygen (N-O) atoms. Hence, the CNO- lewis structure has 180 degree bond angle within all atoms present in it.

CNO- solubility

Fluminate ion (CNO-) is insoluble in

  • Nitric acid
  • Cold water

Fluminate ion (CNO-) soluble in

  • Alkyl chlorides
  • Ammonia
  • Alkyl cyanides
  • Potassium iodide
  • Pyridine
  • Hot water (slightly soluble)

Is CNO- ionic?

Yes, CNO- ion is ionic molecule as it has a negative charge present on it, it is an anion.

Why CNO- ionic?

Fluminate ion (CNO-) is ionic as it is an unstable form of molecule which much greater formal charge is present on it. Also it has multiple bond i.e. triple bond and double bonds in it resonance structure. Thus it can form ions easily. So CNO- is an ionic compound.

How CNO- ionic?

CNO- ion does not have strong covalent bond present on it. It has the capacity to form ion, even its stable form of resonance structure do not have zero formal charge. Rather it has multiple bond with non – zero formal charge and also lone electron pairs are present on it.

Thus it also contains overall negative charge on it. Hence, the bonds can easily break down of CNO- ion and forms ion due to which it is being an ionic compound or an anion.

Is CNO- acidic or basic?

CNO- ion is a conjugate base in nature as it contains lone electron pair to it can accept H+ ion or protons from other molecules.

Why CNO- is basic?

CNO- is basic as it has sufficient number of lone electron pairs to donate to other conjugate acids or molecules. Also it can form the compound like HCNO by accepting proton from other acid compounds. Thus CNO- is a basic ion.

How CNO- is basic?

Fluminate ion or CNO- ion when reacts with water it is slightly miscible with hot water. It can form HCNO compound when react with water by accepting hydrogen atom by donating it electrons to other acidic compounds. Thus it is a conjugate base.

Is CNO- polar or nonpolar?

Yes, CNO- is a polar molecule.

Why CNO- is polar?

CNO- ion has linear molecular shape and geometry, in which there is a symmetrical arrangement of atoms. Thus it is a polar molecule.

How CNO- is polar?

The electronegativity difference is more between central N atom and bonded C and O atoms. Thus the dipole is developed between the molecules due to more electronegativity difference being the CNO- polar in nature.

Is CNO- tetrahedral?

No, CNO- is not tetrahedral. The geometry of CNO- ion is linear so it cannot be tetrahedral.

Why CNO- is not tetrahedral?

As the molecular shape and geometry of CNO- is linear thus it is not tetrahedral.

How CNO- is not tetrahedral?

Tetrahedral geometry needs four bonded atoms, in CNO- ion there is only two bonded atoms to central atom and having linear geometry. Thus it is not tetrahedral.

Is CNO- linear?

Yes, CNO- is linear ion. All the C, N and O atoms are arranged in a single linear line, thus it is linear in shape.

Why CNO- is linear?

CNO- ion follows AX2 generic formula of VSEPR theory thus it is a linear ion.

How CNO- is linear?

The central nitrogen atom of CNO- ion is bonded with only two atoms C and O with no lone pair electrons thus it is a linear ion.

Conclusion:

CNO- lewis structure has total 16 valence electrons with six lone electron pairs. It has three resonance structures. It has linear shape and sp hybridization with 180 degree bond angle. It is an ionic compound and acts as a conjugate base. It is a polar ion.

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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