LiH Lewis Structure & Characteristics (13 Complete Facts)

LiH or lithium hydride is an alkali metal hydride having a molecular weight of 7.95 g/mol. We will learn more details about LiH in this article.

LiH appears as a gray or colorless solid molecule. It is insoluble but reactive with organic protic solvent and soluble in different molten salt but non-reactive to them. It is highly conductive in nature and the value of thermal conductivity of the molecule is 0.125 W/(cm·K) for the solid crystal.

It is diamagnetic in nature and soft material with compressive creep and band gap. Now we discuss the structure, hybridization, polarity, ionic nature, and solubility of LiH in the following part with proper explanation.

1.     How to draw LiH 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 LiH.

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 LIH is 2, and there is one from Li and one for H, we just added them together.

Choosing the central atom

In the 2^nd step for the lewis, structure drawing is chosen the central atom. In the LiH molecule, Li 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 LiH are 4, two for Li, 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 remaining electrons are used in the 2/2 = 1 bond via satisfying the valency. Li 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 LiH molecule, there are no lone pairs present either over Li or H because they have one electron.

2.     LiH 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 the total valence electrons for LiH.

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.

• The electronic configuration of the H is 1s¹
• So, the valence electrons present over the H atom is 1, as 1s is the valence orbital of H
• The electronic configuration of the Li is [He]2s¹
• So, the valence electrons present over the Li atom is 1, because the valence orbital for Li is 3s orbital.
• So, the total number of valence electrons for the LiH is 1+1 = 2

3.     LiH lewis structure 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 LiH.

The number of lone pairs present over the LiH molecule is zero because it has not any lone pairs. The constituent atoms both Li 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 number of lone pairs is calculated by the formula, lone pairs = electrons present in the valence orbital – electrons involved in the bond formation
• The lone pairs present over the Li atom are, 1-1=0
• The lone pairs present over the H atom is, 1-1 = 0
• So, the total number of lone pairs present over the LiH molecule is 0+0 = 0

4.     LiH 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 LiH or not.

In the LiH octet rule is applied although Li and H are both s block elements. The electronic configuration of the H and Li is 1s¹ and [He]2s¹ 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 Li and H to form a bond and complete the octet.

5.     LiH 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 LiH.

The molecular shape of the LiH is linear around the central Li and terminal H atoms which can be predicted from the following table.

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.     LiH 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 LiH molecule.

LiH 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 Li and H.

• 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 Li is unhybridized but due to linear geometry, it adopts sp hybridization.
• The central atom Li is sp hybridized, so the s character here is 1/2^th
• So, the bond angle is, COSθ = {(1/2)} / {(1/2)-1} =-( 1)
• Θ = COS^-1(-1/2) = 180⁰

7.     LiH 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 LiH atom.

The formal charge of LiH is zero because apparently, it appears as neutral, but there is a charge present on the Li 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 = N_v – N_l.p. -1/2 N_b.p
• The formal charge present over the Li 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 LiH molecule.

8.     LiH hybridization

The central atom undergoes hybridization to form a hybrid orbital of equivalent energy from the atomic orbitals. Let us know about the hybridization of LiH.

The central Li is sp hybridized in the LiH molecule which can be confirmed by the following table.

• We can calculate the hybridization by the convention formula, H = 0.5(V+M-C+A),
• So, the hybridization of central Li is, ½(3+1+0+0) = 2 (sp)
• One s orbital and one orbital of Li is involved in the hybridization.
• The lone pairs over the atoms are not involved in the hybridization.

9.     LiH solubility

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

LiH is soluble in water because it can be ionized to form two ions and those ions are soluble in water. Actually, when LiH is dissociated into the ions it forms Li⁺ 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, LiH is soluble in the following solvents

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

10. Is LiH solid or liquid?

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

LiH 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 LiH molecule is higher which means it exists in solid crystal form at room temperature.

11. Is LiH polar or nonpolar?

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

LiH 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 Li to H. so, it has some resultant dipole-moment value and makes the molecule polar.

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

12. Is LiH 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 LiH is basic or not.

LiH 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.

13. Is LiH electrolyte?

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

LiH is a strong electrolyte because when it dissociates into an aqueous solution it formed Li⁺ 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 LiH ionic or covalent?

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

LiH is an ionic molecule because the molecule is formed by the electron donation and acceptance mechanism not by sharing. Also, Li⁺ 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

LiH 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.  I

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Biswarup Chandra Dey

Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. 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.