NaOH Lewis Structure& Characteristics: 17 Complete Facts


NaOH is a strong inorganic base with 40 g/mol molar mass. Let us discuss more NaOH in the following article.

NaOH is an alkali metal base, so the nature of the base is very strong. It is an ionic molecule rather than a covalent because the bond formed by the molecule is the total transfer of electrons. O is sp3 hybridized here with two pairs of lone pairs. The H is attached to the O atom and increases its basicity.

As it is a strong base, it can neutralize strong acids like H2SO4 or HCl to form salt and water. In this article, we can explore more about NaOH bonding mode, structure, basicity, and other important facts in detail.

1.      How to draw the NaOH lewis structure?

Lewis structure of a covalent molecule can give a brief idea about the molecular property. In the following section, we draw the lewis structure of NaOH in a few steps.

Counting the valence electrons

First of all, the total valence electrons of NaOH should be counter which is 8. These are the total value of valence electrons of each atom present in the NaOH. O has six and Na and H have 1 electron in their valence orbital.  We just add those electrons to get the total value of valence electrons of NaOH.

Choosing the central atom

In the second step, we have identified the central atom among three atoms. The central atom should be selected based on electronegativity and size. Among Na, H, and O, O is the most electronegative and the size of the O is larger than the other two. So, O is selected as the central atom here.

Satisfying the octet

For every s block element to obey the octet, they need two electrons in their valence orbital; for p block elements, they need eight electrons. O is a p block element so it needs eight and for H and Na they need two electrons. So, to satisfy the octet total number of electrons required will be 8+2+2=12.

Satisfying the valency

To satisfy the valency of each atom we should add bonds that are coming from those remaining electrons from the octet electrons required and the total valence electrons present. So, the bond required here is ½(12-8) =2. One bond is present between O and Na and the other is between O and H to satisfy the valency.

Assign the lone pairs

After satisfying both the octet and valency we should check the presence of extra non-bonded electrons of the valence orbital of each atom. Only O has four extra nonbonded electrons present after forming two bonds. Those electrons are the non-bonded electrons for O and assign as two pairs of lone pairs.

2.      NaOH valence electrons

Valence electrons are those electrons present in the outermost orbital of each atom and are involved in bond formation. Let us discuss the valence electrons of NaOH.

The total valence electrons of NaOH are 8. This is the summation of O, Na, and H atoms’ valence electrons. These numbers are coming from their respective outermost electronic configuration. The number of valence electrons present in the valence shell is confirmed by the electronic configuration of each atom.

Let us calculate the number of total valence electrons for NaOH.

  • The number of valence electrons for O is 6
  • The number of valence electrons for Na is 1
  • The number of valence electrons for H is 1
  • So, the total number of valence electrons for the NaOH is 6+1+1+ = 8.

3.      NaOH lewis structure shape

The shape of the covalent molecule as per VSEPR theory and for an ionic compound is responsible for the lattice structure. Now explore the shape of the molecule.

The shape of the NaOH molecule is bent with two pairs of lone pairs. This geometry is deviated from the actual geometry of tetra coordinate molecule according to the VSEPR (Valence Shell Electrons Pairs Repulsion) theory. Here two pairs of lone pairs are thought of as two atoms along with two other bond pairs.

The geometry of the molecule although tetrahedral but shape is bent like a water molecule. The lone pairs of the molecule are responsible for the bent shape. Due to lone pairs – bond pair repulsion the shape is changed to bent just like a water molecule.

4.      NaOH lewis structure lone pairs

Non-bonded electrons are present in the valence shell of each respective atom and not involved in the bond pairs. Let us discuss more lone pairs of NaOH.

Only O contains the lone pairs in the NaOH molecule. Because it has six electrons in its outermost orbital as a group 16th element, after forming two bond pairs, it has four non-bonded electrons which exist as lone pairs. Na and H both are group IA elements so they have only one electron and lack lone pairs.

  • Let us calculate the lone pairs of each atom in NaOH by the formula, Lone pairs = valence electrons – bonded electron.
  • The lone pairs present over the Na is, 1-1 =0
  • The lone pairs present over the H is, 1-1 = 0
  • The lone pairs present over the O are, 6-2 = 4
  • So, O has 4 non-bonded electrons, meaning it has two pairs of lone pairs.

5.      NaOH lewis structure angle

Lewis structure or bond angle is the particular angle which makes by the atoms in a molecule by their absolute arrangement.  Let us find the bond angle of NaOH.

The bond angle value for NaOH is near about 1040. The value is less than a tetrahedral angle value, but due to lone pairs repulsion, the shape is changed as well as the bond angle too. This angle is quite similar to a water molecule as a water molecule has a bent shape due to lone pairs repulsion.

To minimize the lone pairs – bond pairs repulsion NaOH decreases its bond angle from 109.50 which is the true value for the tetrahedral molecule. Due to lone pairs repulsion, the shape is changed for the molecule, and for this reason, the bond angle is changed to 1040.

6.      NaOH lewis structure octet rule

Every atom in a particular molecule tries to complete its octet by fulfilling the valence orbitals. Let us understand the octet of NaOH in the following section.

To complete the octet O formed two single bonds with H and Na atoms respectively. In this way, it has shared four electrons and already it has four electrons in its outermost orbital. Again, Na and H both share one single bond to complete their octet. The needs of electrons are only two here.

Eight electrons are accumulated by the p block element as per octet. The electronic configuration of p block element O is [He]2s22p4. There are a maximum of six electrons that can be lied in the p orbital, so only two electrons are required. For s block elements like Na and H, they need only one electron.

7.      NaOH lewis structure formal charge

The amount of charge present over which atom can be predicted with the help of the formal charge concept. Let us calculate the formal charge of NaOH.

The value of the formal charge of NaOH is zero. Because it is a neutral molecule and all the charge and valency of the molecule are fully satisfied. The electronegative di-valency of O is satisfied by the two electropositive monovalent Na and H atoms. So, there is not possible to present any kind of charge.

  • We have to assume the same electronegativity for all the atoms. Now calculate the formal charge of each atom separately by the formula F.C. = Nv – Nl.p. -1/2 Nb.p.
  • The formal charge over the O atom is,6-4-(4/2)=0
  • The formal charge over the Na atom is,1-0-(2/2)=0
  • The formal charge over the H atom is,1-0-(2/2)=0

8.      NaOH lewis structure resonance

Resonance is the hypothetical concept by which electron clouds are delocalized among different skeleton forms of the molecule. Let us understand the resonance of NaOH.

There is no resonance observed in the NaOH molecule. Because there is the absence of enough electron clouds which can be delocalized in between the molecules. So, there is no skeleton form observed. O has lone pairs being an electronegative atom it could not donate electron density to other atoms.

The electron density flows from the Na and H to the electronegative O atom. In another word, O pulls the electron density from the electropositive Na and H atoms by the sigma bonds. So, only the sigma electron density is being dragged away from the electropositive atoms to the O site only.

9.      NaOH hybridization

By mixing the atomic orbitals of different energy to get a hybrid orbital of equivalent energy is called hybridization. Now discuss the hybridization of NaOH in detail.

From the below table of hybridization, it is predicted that NaOH is sp3 hybridized.

Structure  Hybridization valueHybridization state    Bond angle
1.Linear   2sp /sd / pd   1800
2.Planner trigonal  3sp2      1200
3.Tetrahedral  4sd3/ sp3   109.50
4.Trigonal bipyramidal5sp3d/dsp3       900 (axial), 1200(equatorial)
5.Octahedral 6sp3d2/ d2sp3     900
6.Pentagonal bipyramidal7sp3d3/d3sp3    900,720
Hybridization table

The hybridization of the central O in the NaOH is calculated by the following formula, H = 0.5(V+M-C+A), where H= hybridization value, V is the number of valence electrons in the central atom, and M = monovalent atoms surrounded. From the above formula, the hybridization value of central O is sp3 in NaOH.

10. Is NaOH a solid?

When a molecule is held by a strong attraction force like Van der Waal’s force or dipole-dipole force then it is called solid. Let’s see whether NaOH is solid or not.

NaOH is a solid molecule because it is held by strong Van Der Waal’s force of attraction. Besides this, it is also held by London dispersion force and due to its ionic nature, there is also observed ionic interaction between Na+ and OH- which is strong enough. It has a higher melting point, so NaOH is solid.

Why and how NaOH is solid?

The stronger lattice energy of NaOH makes the molecule solid at room temperature. The molecule has a higher boiling point because due to the higher van der Waal’s force of attraction so, it required more energy to break the bond. So, NaOH has a higher boiling point which indicates its solid nature.

11. Is NaOH soluble in water?

Any polar or ionic molecule is soluble in water by ionization via H-bonding with the water molecule. Let’s see whether NaOH is soluble in water or not in the next part.

NaOH is soluble in water due to its polarity and ionic nature. It can easily be ionized in Na+ and OH and gets soluble in water. Those small-sized ions are gets dissolved in water very quickly. Also, its hydration energy is very high than its lattice energy so it helps to quickly and fast soluble in water.

Why and how NaOH is soluble in water?

As NaOH is polar so it has a solubility in polar solvents like water. We know like dissolved like that means polar molecule always soluble in a polar solvent. Also, when it is ionized then OH ion can form H-bond with water molecules which are more favorable for solubility in water.

12. Is NaOH a molecular compound

A molecular compound is a mixture of atoms with a fixed ratio to maintain valency and held together with a bond. Let’s see whether NaOH is a molecular compound or not.

NaOH is a molecular compound because it follows all the criteria of a compound. The valency of Na, H, and O are fully satisfied and they are bonded with an ionic interaction and ionic bond. The ratio of each atom is always fixed because if the ratio is changed for any atom then it will no longer be a molecule.

Why and how NaOH is a molecular compound?

Each atom in the NaOH is attached by the ionic bond or van der Waal’s attraction force. The ratio of Na, O, and H is always maintained which is 1 for the molecule. Here bi valency of O is satisfied by the two sigma bonds and also mono valency for H and Na is also satisfied by the one bond formation.

13. Is NaOH polar or nonpolar?

The presence of permanent dipole-moment and also observed electronegativity difference makes a molecule polar. Let us see whether NaOH is polar or not in the coming part.

NaOH is a polar molecule because it has a resultant dipole moment. Also, there is the presence of electronegative O atoms, so the electronegativity difference between O and electropositive Na and H atoms is also observed. Due to the ionic nature of the bond, there is some polar character in the Na-OH bond.

Why and how NaOH is polar?

In NaOH the dipole-moment flows from electronegative O to electropositive Na and H atoms. Although the magnitude of the dipole moment is equal due to asymmetric shape there is present a permanent dipole-moment value. Again, its solubility in water molecules also indicates the polarity nature of the molecule.

14. Is NaOH an acid or base?

In the aqueous solution releasing of OH ion is known as base and releasing of H+ is known as acid according to Arrhenius’s theory. Let’s see whether NaOH is acid or base.

NaOH is a strong base because it can release OH- ion very easily when it gets dissolved in the aqueous solution. From the value of pkb we can say that the nature of this base is very strong, it can neutralize strong acids like H2SO4, HCl, etc. Due to availability of OH- it can accept acidic proton easily.

Why and how NaOH is a base?

When NaOH is ionized in the aqueous solution then it can form Na+ and OH-. The OH- can accept a proton from the acidic molecule and can neutralize that acidic species. Also, it is an alkaline hydroxide which is basic in nature due to the presence of alkali metal ions. Also, pH value of NaOH is very high.

15. Is NaOH an electrolyte?

A species gets dissolved in an aqueous solution to ionize in the ions and carry electricity is known as an electrolyte. Let’s see whether NaOH is an electrolyte or not.

NaOH is electrolye because it ionized Na+ and OH when it gets dissolved in the water solution and carries electricity. Due to the presence of a charged particle, it can easily conduct electricity by the solution and behave as an electrolyte. The method of ionization makes the solution charged.

Why and how NaOH is a strong electrolyte?

Due to ionization NaOH is ionized to Na+ and OH. Those ions have small in size and higher charge density and also higher mobility. Due to those reasons, the ionized solution becomes more chargeable. NaOH is ionized in the aqueous solution in a very faster way which makes it a strong electrolyte.

16. Is NaOH a salt?

A molecule has a cation and an anion attached by ionic interaction is called salt, but cation and anion is should not be H+ and OH-. Now see if NaOH is salt or not.

NaOH is not salt because it has the basic anion OH. Although it has a cation Na+ it is the counter ion of the hydroxide anion. Salt is formed due to the reaction between acid and base molecules. But NaOH itself is a strong base and reacts with the acid molecule to form a salt.

Why and how NaOH is not a salt?

NaOH has two ions one is Na+ cation and the other is OH anion. Although it has a cation other than H+ it has anion OH. So, NaOH is not formed by the reaction with acid and base molecules, unlike salt. NaOH can also neutralize acid molecules by hydroxide and it is formed via ionic interaction but not salt.

17. Is NaOH ionic or covalent?

No molecule is pure ionic or covalent, every ionic molecule has a covalent character or vice versa – Fajan’s rule. Let’s discuss whether NaOH is covalent or ionic.

NaOH is an ionic molecule because the bond presence between Na and OH is formed by the total electron shared by Na. again, the charge density of the Na+ ion is very high and the size is also small so its ionic potential is high and also OH is a larger anion that can easily be polarized by the cation

Why and how NaOH is ionic?

According to Fajan’s rule of polarizability, the cation is polarized anion very easily. Also, the bond present between two ions is highly ionic in nature so we can say that the atoms are held by the ionic interaction between them. Again, its lattice energy and hydration energy are also high like ionic molecules.

Conclusion

NaOH is an alkali metal hydroxide and a strong monoacidic base. It has one replaceable hydroxide ion is present so it can neutralize monobasic acid by one molecule. It is a high ionic compound and soluble in water having a higher polarity.

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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