NaH Lewis Structure & Characteristics (15 Helpful Facts)


NaH or sodium hydride is one of the strongest inorganic bases having a molecular weight of 23.998 g/mol. Now we will discuss about the NaH in detail.

NaH is the alkali metal hydride of Na, H is in -1 oxidation state here, so it is a good reducing agent and can reduce main group elements like S-S or Si-Si bonds easily. It also acts as a Bronsted base towards Bronsted acid molecule and also in organic chemistry it can be acidified with many functionalities.

NaH is an ionic inorganic basic molecule and it can be ignited in the air spontaneously. It can deprotonate the carbon-containing acid molecules. Now we can discuss the lewis structure, bonding, octet rule, polarity, and basicity of the NaH with proper explanation in the following part.

1.     How to draw NaH lewis structure?

With the help of lewis structure, we can predict the valence electrons, lone pairs, and other properties related to a molecule. Let us draw the lewis structure of NaH.

Counting the valence electrons

For drawing lewis structure of a molecule we have to count the total valence electrons of the molecule by counting the valence electrons of the substituent atoms. The total valence electrons present in the NaH is 2, and there is one from Na and one for H, we just added them together.

Choosing the central atom

In the 2nd step for the lewis, structure drawing is chosen the central atom. In the NaH molecule, Na is chosen as the central atom because it is more electropositive than H and also larger in size than H. Surrounding the atom is connected through the bond with the central atom in the molecule.

Satisfying the octet rule

Each atom in a molecule should obey the octet rule during the bond formation via completing their valence electrons with a suitable number of electrons. The electrons required for the octet in the NaH are 4, two for Na, and two for H as they belong to the s block element and it accumulates two electrons.

Satisfying the valency

During the bond formation, each atom should be satisfied by valency. The electrons required for the octet are 4 and the available valence electrons are 2, so the remaining electrons are used in the 2/2 = 1 bond via satisfying the valency. Na and H both have valency 1 and they formed only one bond between them.

Assign the lone pairs

Lone pairs exist only those cases if there are more valence electrons present in the valence orbital of any atom than its bond participation electrons. In the NaH molecule, there are no lone pairs present either over Na or H because they have one electron.

2.     NaH valence electrons

The electrons present in outer shell of any atom and responsible for the chemical nature of the atom are called valence electrons. Let us count valence electrons of NaH.

The total number of valence electrons present in the outermost shell of NaH is 2. Where one electron comes from the Na site and one electron comes from the H site because they have only one valence electron in their outermost shell. So, we just added the individual valence electrons of each atom separately.

  • The electronic configuration of the H is 1s1 because it is 1st element in the periodic table.
  • So, the valence electrons present over the H atom is 1, as 1s is the valence orbital or outermost shell of H
  • The electronic configuration of the Na is [Ne]3s1 because it is an s block element.
  • So, the valence electrons present over the Na atom is 1, because the valence orbital for Na is 3s orbital.
  • So, the total number of valence electrons for the NaH is 1+1 = 2

3.     NaH lewis structures lone pairs

The lone pairs are those valence electrons present over the valence orbital as remaining after forming the bond. Let us count the total number of lone pairs of NaH.

The number of lone pairs present over the NaH molecule is zero because it has not any lone pairs. The constituent atoms both Na and H have only one electron in the valence orbital of them and that one electron is used in the bond formation so, they have zero electrons left.

  • The formula is used for the calculation of the number of lone pairs, lone pairs = electrons present in the valence orbital – electrons involved in the bond formation
  • The lone pairs present over the Na atom are, 1-1=0 (Na has one valence electron and one bonding electron)
  • The lone pairs present over the H atom is, 1-1 = 0 (H has only one valence electron and one bonding electron)
  • So, the total number of lone pairs present over the NaH molecule is 0+0 = 0

4.     NaH lewis structure octet rule

The octet rule is the completion of the valence orbital by suitable numbers of electrons during the bond formation. Let us check whether octet is applied to NaH or not.

In the NaH octet rule is applied although Na and H are both s block elements. The electronic configuration of the H and Na is 1s1 and [Ne]3s1 respectively. So, both have only one electron in s orbital and can accept one more electron because in the s orbital maximum number of electrons will be present at two.

So, the required number of electrons for completion of the octet is 4 and the valence electrons available are two. So, to accumulate the remaining electrons by the 2/2 = 1 bond and there must be one bond minimum present between Na and H to form a bond and complete the octet.

5.     NaH lewis structure shape

The molecular shape of the molecule is an arrangement of the central atom with other atoms in a geometry. Let us predict the molecular shape of the NaH.

The molecular shape of the NaH is linear around the central Na and terminal H atoms which can be predicted 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
NaH Molecular Shape

The molecular shape of an ionic molecule is determined by the crystal structure and the covalent molecule is predicted by the VSEPR (Valence Shell Electrons Pair Repulsion) theory, and according to this theory, the AX type of molecule having geometry is linear.

6.     NaH lewis structure angle

The bond angle is the angle made by the atoms in a particular shape for proper orientation in that arrangement. Let us calculate the bond angle for the NaH molecule.

NaH has linear geometry so it has a bond angle of 1800 because for a linear geometry the bond angle is always 1800 from the mathematical calculation. There is no steric repulsion present so there is no chance for deviation of the perfect bond angle for the linear molecule between Na and H.

NaH Bond Angle
  • Now we merge the theoretical bond angle with the calculated bond angle value by the hybridization value.
  • The bond angle formula according to Bent’s rule is COSθ = s/(s-1).
  • The Na is unhybridized but due to linear geometry, it adopts sp hybridization.
  • The central atom Na is sp hybridized, so the s character here is 1/2th
  • So, the bond angle is, COSθ = {(1/2)} / {(1/2)-1} =-( 1)
  • Θ = COS-1(-1/2) = 1800

7.     NaH lewis structure formal charge

With the help of formal charge can predict partial charge present over each atom in a molecule by equal electronegativity. Let us predict formal charge of the NaH atom.

The formal charge of NaH is zero because apparently, it appears as neutral, but there is a charge present on the Na and H atom. those charges are equal in magnitude but opposite in direction, so they can be canceled out and make the molecule neutral. So, predict that partial charge present over each atom.

  • 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 Na atom is 1-0-(0/2) = +1
  • Th formal charge present over the H atom is 0-1-(0/2) = -1
  • So, each cation and anion carry one charge and the value is the same but they are opposite in nature and cancel to make the formal charge zero for the NaH molecule.

8.     NaH hybridization

For covalent molecules, the central atom undergoes hybridization to form a hybrid orbital of equivalent energy. Let us know about the hybridization of NaH.

The central Na is sp hybridized in the NaH molecule which can be confirmed by 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 Na is, ½(3+1+0+0) = 2 (sp)
  • One s orbital and one orbital of Na is involved in the hybridization.
  • The lone pairs over the atoms are not involved in the hybridization.

9.     NaH solubility

Most of the ionic molecule is soluble in water as they can be dissociated and gets soluble in water. Let us see whether NaH is soluble in water or not.

NaH is soluble in water because it can be ionized to form two ions and those ions are soluble in water. Actually, when NaH is dissociated into the ions it forms Na+ and this ion can attract the water molecule surrounding by its ionic potential, and the hydride ion can form H-bonding with the water molecule.

Apart from a water molecule, NaH is soluble in the following solvents

  • CCl4
  • CS2
  • Benzene
  • Methanol
  • CHCl3
  • Ammonia

10. Is NaH solid or gas?

Ionic compounds are mostly solid in nature because they have a proper crystal structure and strong bonding. Let us check whether NaH is solid or not.

NaH is a solid molecule having face center cubic crystal and the energy of the crystal is very strong to stay in solid form. Due to presence of the crystal, the entropy is very low for the molecule, and for this reason, all the atoms are closely packed in the crystal. It appears as a grey crystalline solid.

The lattice constant for the NaH molecule is higher which means it exists in solid crystal form at room temperature.

11. Is NaH polar or nonpolar?

Ionic compounds are polar in nature due to the bond formation between them being polar in character. Let us check whether NaH molecule is polar or not.

NaH is a polar molecule because there is sufficient electronegativity difference present in two atoms and also being a linear structure there is no way to cancel out the dipole-moment from Na to H. so, it has some resultant dipole-moment value and makes the molecule polar.

Also, the bond formed between Na and I is by the donation of electrons and due to electronic interaction, the bond has a more polar character.

12. Is NaH acidic or basic?

If a molecule can release a proton or hydroxide ions in an aqueous solution then it is called acid or base respectively. Let us check whether NaH is basic or not.

NaH is a strong base although it does not have H+ or OH it has a hydride ion that can draw the proton from other subsequent and form conjugate acid. hydride ion has a higher affinity to draw the proton to form a hydrogen molecule and behaves as a strong bronsted base.

Even in reverse NaH where the molecule dissociates Na and H+ and due to the formation of proton it behaves as strong acid.

13. Is NaH electrolyte?

Ionic molecules have higher electrolytic nature because they are formed by the strong interaction of ions. Let us see whether NaH is an electrolyte or not.

NaH is a strong electrolyte because when it dissociates into an aqueous solution it formed Na+ and H, which are strong ions and the mobility of those ions is very high. The ionic potential also those ions are very higher and carry electricity through the aqueous solution very fast.

14. Is NaH ionic or covalent?

The ionic molecule has strong interaction between constituent atoms and has higher polarizing power. Let us see if NaH is ionic or not.

NaH is an ionic molecule because the molecule is formed by the electron donation and acceptance mechanism not by sharing. Also, Na+ has higher ionic potential due to charge density so it can polarize the anion easily and hydride ion has greater polarizability according to Fajan’s rule it is an ionic molecule.

Conclusion

NaH is a strong inorganic Bronsted base and it can be used in many organic reactions to pull out the acidic proton from the desired molecule.  It can also be used as hydrogen storage in a fuel cell.

Biswarup Chandra Dey

Hi......I am Biswarup Chandra Dey, I have completed my Master's in Chemistry. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.

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