Na3N Lewis Structure & Characteristics (13 Complete Facts)

Na3N or sodium nitride is the ternary nitride of alkali metal compound having a molecular weight of 82.97 g/mol. Now we will discuss Na3N in detail.

Na3N can be thought of as an ammonia molecule where all the three H atoms are replaced by the three sodium atoms. The arrangement of the molecule is like ammonia, which is a tetrahedral moiety. The lone pairs of N are also involved in the geometry as well as hybridization. It appears dark blue in color.

It can be synthesized by the thermal decomposition of NaNH2 or normal reaction between Na and N atoms. In this article, let us explain the molecular property of NaN3 along with its hybridization, solubility, polarity, and bond angle with a proper explanation in the following section of the article.

1.     How to draw Na3N lewis structure

Lewis structure can give us a proper idea about the bonding, valence electrons, shape, and bond angle. Now we try to draw the lewis structure of Na3N in a few steps.

Counting the total number of valence electrons

Electrons are involved in the valence orbital and bond formation for the Na3N, on the other hand, we can say each Na and N contributed a total of 8 valence electrons for the molecule which is responsible for the chemical property of the molecule.

Choosing the central atom

After counting the total valence electrons, we need to choose the central atom for the molecule. Choosing a central atom is a very important part because all the surrounding atoms are connected to it. Based on size and electronegativity we choose N as the central atom for the Na3­­N molecule.

Satisfying the octet

Every atom in a molecule after bond formation should be satisfied by their octet completion to fulfill their valence orbital and gain noble gas stability. To complete the octet each atom should share or take a suitable number of electrons in valence orbital. The total electrons required as per octet are 14.

Satisfying the valency

Each atom should form an equal number of bonds to its valency. The valence electrons are 8 and octet electrons will be 14, so the remaining 14-8 = 6 electrons should be accompanied by 6/2 = 3 bonds. N has stable valency 3 and forms 3 bonds with three Na atoms and each Na forms a single bond with N.

Assign the lone pairs

There will be a minimum of three bonds present in the Na3N molecule and after that, if electrons are left then are used in bond formation (if required) or exist as lone pairs over particular atoms. Only N contains lone pair because it has five valence electrons and forms three bonds sharing three electrons.

2.     Na3N valence electrons

Valence electrons are those present in the outermost orbital and responsible for the chemical property of an atom. Let us count valence electrons present for NaN3.

The total number of valence electrons is counted to be 8 where electrons contribute from the 3 Na atoms and 1 N atom also. So, the total valence electrons are the summation of the valence electrons for the individual atoms. We have to count valence electrons of individual atoms and then add together.

  • The electronic configuration of Na is [Ne]3s1
  • So, the valence electron for each Na atom is 1
  • The electronic configuration of N is [He]2s22p3
  • So, the electronic configuration for the N atom is 5
  • So, the total valence electrons for the NaN3 are (1*3) + 5 =8

3.     Na3N lewis structure lone pairs

The number of lone pairs is the remaining electrons from the valence electrons to bond participating electrons. Let us calculate the lone pairs of Na3N.

The total lone pairs present over the Na3N is 1 pair which means only 2 lone pair electrons and those electrons are from the valence orbital of N. because N has 5 electrons including its both valence orbital and only three electrons are used in the bond formation, so remaining electrons exist as lone pair.

  • The formula to be calculated for the lone pairs is, lone pairs = electrons present in the valence orbital – electrons involved in the bond formation
  • The lone pairs present over each Na atom is, 1-1 = 0
  • The lone pairs present over the N atom are, 5-3 = 2
  • So, N contains only 1 pair of electrons and that is the total lone pairs over the NaN3 molecule.

4.     NaN3 lewis structure octet rule

After bond formation, the octet rule is applied to the molecule by completing the valence orbital with a suitable number of electrons. Let us check the octet of NaN3.

For the completion of octets, Na and N need one and three electrons respectively because they have one and five valence electrons in their valence orbital. So, the total electrons required for the octet are, 6+8 = 14 but valence electrons are available at 8, so the remaining electrons are filled by the octet.

There will be 14-8 = 6 electrons shared by the 6/2 = 3 bonds needed for the NaN3 molecule and each Na makes a single bond with N this way N makes three single bonds to complete the octet of N and Na. So, by sharing electrons, each atom in the NaN3 completed its valence orbital and octet.

5.     NaN3 lewis structure shape

The molecular shape of NaN3 is determined by the VSEPR theory and the presence of the central and other atoms. Let us predict the shape of the NaN3.

The molecular shape of the NaN3 around the central N atom is trigonal pyramidal which can be determined from the following table.

Molecular
Formula
No. of
bond pairs
No. of
lone pairs
Shape  Geometry    
AX10Linear  Linear
AX2        20Linear  Linear  
AXE       11Linear  Linear  
AX330Trigonal
planar
Trigonal
Planar
AX2E     21BentTrigonal
Planar
AXE2     12Linear  Trigonal
Planar
AX440TetrahedralTetrahedral
AX3E     31Trigonal
pyramidal        
Tetrahedral
AX2E2                2BentTetrahedral
AXE3                     13Linear  Tetrahedral
AX550trigonal
bipyramidal
trigonal
bipyramidal
AX4E     41seesawtrigonal
bipyramidal
AX3E2    32t-shaped         trigonal
bipyramidal
AX2E3    23linear   trigonal
bipyramidal
AX660octahedraloctahedral
AX5E     51             square
pyramidal   
octahedral
AX4E2                    42square
pyramidal 
octahedral
VSEPR Table
Screenshot 2022 09 23 210139
NaN3 Molecular Shape

The shape of the tetra coordinated molecule is tetrahedral where repulsion is very minimal, but if one bond is replaced by lone pairs then shape will be changed to trigonal pyramidal like AX3E type molecule as per VSEPR (Valence Shell Electrons Pair Repulsion) theory, NaN3 adopted trigonal pyramidal shape.

6.     Na3N lewis structure angle

The bond angle of the Na3N depends on the orientation of the N and three Na atoms in a trigonal pyramidal shape. Let us calculate the bond angle of the Na3N.

The bond angle Na-N-Na is around 1070, due to the three bond pairs and one lone pair repulsion, the molecule decreases its bond angle from the ideal value of 109.50. the shape of the molecule has deviated from the ideal shape of tetrahedral to trigonal pyramidal, so the bond angle is also changed.

Screenshot 2022 09 23 210128
NaN3 Bond Angle
  • Now we try to merge the theoretical bond angle with the calculated bond angle value from its hybridization of the central atom.
  • The bond angle formula according to Bent’s rule is COSθ = s/(s-1).
  • The central atom N is sp3 hybridized, so the s character here is 1/4th
  • So, the bond angle is, COSθ = {(1/4)} / {(1/4)-1} =-( 1/3)
  • Θ = COS-1(-1/2) = 109.50
  • But the shape of the molecule changes so the bond angle is also decreased.
  • So, the value of the bond angle is calculated value and the theoretical value is equal.

7.     Na3N lewis structure formal charge

The formal charge is a hypothetical concept by assuming equal electronegativity for all atoms to predict the charge. Now we calculate the formal charge of Na3N.

The formal charge shown by the Na3N molecule is 0 because the molecule Na3N is neutral in nature. The charge accumulated by the cation as well as anion is fully neutralized in this molecule. The electropositive Na atoms are neutralized by electronegative nitrogen atoms by the charge of valency.

  • The molecule is neutral on the calculation of formal charge by the formula, Formal charge = Nv – Nl.p. -1/2 Nb.p
  • The formal charge present over the Naatom is 1-0-(2/2) = 0
  • The formal charge present over the Iodide ion is, 5-2-(6/2) = 0
  • So, the formal charge of Na and Nare 0 and 0 respectively, so the value is the same and zero, so they neutralized each other and make the molecule neutral

8.     Na3N hybridization

The central atom N undergoes hybridization because it has different orbital of different energy to make a covalent bond. Let us see the hybridization of the Na3N.

N is sp3 hybridized where its lone pairs are present one of hybridized orbital which can be confirmed from the following table.

Structure   Hybridization
value  
State of
hybridization
of central atom
Bond angle
1.Linear         2         sp /sd / pd1800
2.Planner
trigonal      
3sp2                   1200
3.Tetrahedral 4sd3/ sp3109.50
4.Trigonal
bipyramidal
5sp3d/dsp3900 (axial),
1200(equatorial)
5.Octahedral   6        sp3d2/ d2sp3900
6.Pentagonal
bipyramidal
7sp3d3/d3sp3900,720
Hybridization Table
  • We can calculate the hybridization by the convention formula, H = 0.5(V+M-C+A),
  • So, the hybridization of central N is, ½(5+3+0+0) = 4 (sp3)
  • One s orbital and three p orbitals of N are involved in the hybridization.
  • The lone pair over the N is involved in the hybridization.

9.     Na3N solubility

The solubility of the covalent molecule depends on the tendency of H-bonding and the extent of the dissociation. Let us see whether Na3N is soluble in water or not.

Na3N is soluble in water because the presence of the electronegative smaller size N atom can able to form H-bonding with the lone pairs of the water molecule. Also, the cation Na+ can attract the water molecule by its ionic potential and gets soluble in water.

Apart from water Na3N can be soluble in other following solvents

  • CCl4
  • CHCl3
  • DMSO
  • Benzene
  • Toluene

10. Is Na3N solid or liquid?

Most covalent molecules have lower interaction energy between constituent atoms. Now we see whether Na3N is solid or liquid in nature.

Na3N is a solid covalent molecule because van der Waal’s for of attraction in the molecule is very high, so all the atoms exist in close proximity to each other. In the crystal form, it exists as cubic where each Na atom is surrounded by four N atoms, and each N atom is also surrounded by four Na atoms.

At room temperature, it appears as reddish brown or dark blue solid crystal.

11. Is Na3N polar or nonpolar?

The covalent molecule shows both polar and non-polar characters based on the geometry they adopted. Let us see whether Na3N is polar or non-polar.

Na3N is a polar molecule due to its pyramidal shape, which is asymmetrical. Three dipole-moment flow works from the electropositive Na atom to electronegative N atoms exist. But there no opposite direction of dipole-moment will be observed due to molecular shape and showing a resultant dipole-moment.

Screenshot 2022 09 23 210152 1
NaN3 Dipole -Moment

Also, the bond angle between Na and N makes the molecule polar for its orientation.

12. Is Na3N acidic or basic?

The acidity or basicity depends on the ability to donate proton or hydroxide in the aqueous solution. Let us see whether Na3N is acidic or basic.

Na3N is neither acidic nor basic in nature because it is formed by the neutralization reaction between one acid (hydrochloric acid) and one base (sodium hydroxide) compound. So, it does not have any particular character. Even it does not have any acidic proton or hydroxide ion.

But the lone pair over the N can be donated due to the presence of hybridized orbital so can be delocalized and for this reason, it acts as a lewis base.

13. Is Na3N electrolyte?

The electrolytic nature of covalent molecules is low than ionic molecules because they are attracted by a weak force. Let us see whether Na3N is an electrolyte or not.

Na3N is a strong electrolyte because it can dissociate into two highly charged particles Na+ and N3-. Due to the formation of these two types of ions in the aqueous solution, the solution also becomes charged and carries electricity very easily.

14. Is Na3N ionic or covalent?

The nature of the bonding of the central atom depends on the hybridization or strong interaction force. Let us discuss whether Na3N is ionic or covalent.

Na3N is slightly ionic in nature along with a covalent character because no molecule is 100% pure ionic or covalent depending on the theory of polarizability of Fajan’s rule. The central N is undergoing hybridization like a covalent molecule but Na+ has higher ionic potential, can be a polarized anionic part.

Conclusion

Na3N is an inorganic lewis base where the lone pair over the N can be donated to the electron-poor center and participate in the various reaction. It does not have melting point even at higher temperatures it decomposed into black color elemental form.

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