Ca(OH)2 Lewis Structure & Characteristics: 17 Complete Facts

Carbon hydroxide is a chemical substance, and its chemical formula is Ca(OH)2. Let us look at some details regarding the Ca(OH)2.

Ca(OH)2 has a white-coloured, uncommon mineral called portlandite. The molecular weight is 74.09 g/mol and the density is 2.2 g/cm3. It is produced by a heat and hydration process using calcium oxide. It is converted to calcium hydroxide, sometimes known as slaked lime, or Ca(OH)2.

Ca(OH)2 appears colourless when it is crystallised. Other names for this substance include hydrated lime and caustic lime. This section provides a detailed description of Ca(OH)2, lone pairs, their shape, valence electrons, hybridisation, and more.

How to draw Ca(OH)2 lewis structure?

Lewis dot structure is a representation of atoms, lone pairs, molecule form, and valence electrons. Learn to draw the Lewis structure of Ca(OH)2 here.

1. Valence electron count in Ca(OH)2:

Ca(OH)2 lewis structure contains a total of 16 valence electrons. Ca, O, and H are part of groups 2, 16, and 1 correspondingly. Ca, O, and H each have a valence electron that is 2, 6, and 1 accordingly.

2. Central Atom in Ca(OH)2:

In Ca(OH)2, Ca is the central atom because it is electropositive with a +2 charge on it. Hydroxide is the surrounding atom with a Negative charge on it. Formal charges indicate the stability of Ca(OH)2.

3. Assign the electron for bonding in Ca(OH)2:

As Ca(OH)2 is made by the electrostatic force of attraction which means no direct bond between Ca and OH. Hydrogen and oxygen share electrons to form the hydroxide ion.

4. Octet completion in Ca(OH)2: 

As Ca(OH)2 is ionic due to the transfer of two-electron from Ca to the OH, the octet of both atoms is completed. Ca gains the closest (Ar) noble gas configuration when it loses two electrons. 2 OH gains the closest stable noble gas configuration of Ne when it accepted these two electrons from calcium

5. Final lewis structure:

As Ca(OH)2 is not showing sharing of electron or covalent bonding. It is an ionic compound and does not have a particular structure. The lewis dot structure of Ca(OH)2 is given below in the image:

ca(oh)2 lewis structure
Lewis dot structure of Ca(OH)2

Ca(OH)2 lewis structure formal charge

A Lewis structure’s stability is determined by the intrinsic charges of its atoms or molecules. Let us determine the formal charge of Ca(OH)2.

Ca(OH)2 lewis structure has an overall Zero formal charge. Here is the formula for calculating formal charge on Ca(OH)2 Lewis structure: F.C on Ca(OH)2 Lewis structure = Valence electrons on Ca(OH)2 atoms – Unbonded electrons on Ca(OH)2 atoms – 12 bonded electrons on Ca(OH)2 atoms).

The Formal charge table on Ca(OH)2 is shown below:

Atoms involved
in Ca(OH)
Formal charge
Central Atom
Outer Atom
The formal charge on Ca(OH)2 lewis structure, Ca = +2, 2F=-1, (Ca(OH)2=+2 -2=0)

Ca(OH)2 valence electrons

Chemical reactions result in the release of an atom’s valence electrons, or outermost electrons. Calculate the valence electron of the Lewis structure for Ca(OH)2.

Ca(OH)2 has a total of 2 + 14 = 16 valence electrons in its Lewis structure. Here periodic table matters a lot because Calcium belongs to group 2, Oxygen from group 15 and hydrogen from group 1 respectively. 

  • They each have 2 and 6 and 1 valence electrons respectively.
  • Ca has valence electrons= 2*1=2.
  • OH valence electron= 2*(6 +1).
  • The following formula is used to determine the total amount of valence electrons in Ca(OH)2= 2 + 2*(6+1).
  • 2 + 2(7) = 2 + 14 = 16.

Ca(OH)2 lewis structure octet rule

The tendency of an atom to form enough bonds to gain eight valence electrons is known as the octet rule. Let us determine whether Ca(OH)2 complies with the octet rule.

In Ca(OH)2, both the calcium and hydroxide ions completed their octets. To attain the closest noble gas configuration of Ar. Which has 8 electrons in its valance shell, the Ca atom transfers two electrons, Ca+2 =[Ar]3s23p6; so the octet is satisfied.

The OH radical gains these two electrons to form the closest noble gas configuration of Ne. Which also has eight valence electrons (2s22p6); so the octet is satisfied.

Ca(OH)2 lewis structure lone pairs

Lone pair electrons are unshared electrons that are still present in a chemical or molecule after a bond has been formed. Let us study the Ca(OH)2 lone pair electron.

Ca(OH)2 has six lone pairs in total. As there are two bond pairs between calcium and hydroxide ions. No covalent bonding but some forces attract them.

  • Lone pair electrons in Ca(OH)2 = Valence electrons (V.E) – ½ Number of bonds.
  • Lone pair electron on Ca = 2 (V.E) – 2 (Ca – OH bonds) / 2 = 0.
  • Outer OH radical lone pair electron= 7 (V. E) – 1(Ca-OH bond) / 2 = 6 / 2 = 3 for 2OH radicals.
  • Total lone pairs on 2OH ions= 3*2=6.

Ca(OH)2 lewis structure shape

Objects are shaped by their spatial contours, while structures are built and assembled. Let us look at the shape of  Ca(OH)2.

Calcium hydroxide has a hexagonal-shaped crystal structure. Ca(OH)2 emphasises that there are two OH anions that connect with each Ca2+ cation through electrostatic attraction. 

  • The difference in electronegativity between Ca and O prevents a strictly covalent connection between the two.
  • This hexagonal structure of Ca(OH)2 appears to have a polymeric structure since the ions in the crystal are so close together.
  •  The image is shown below for the hexagonal structure of Ca(OH)2:

Ca(OH)2 lewis structure angle

The molecular makeup and form of a molecule determine its bond angles. Let us talk about the Ca(OH)2 molecules bond angle.

The bond angle in the Lewis structure Ca(OH)2 is 180°. The VSEPR theory of molecular structure assigns the Ca(OH)2 Lewis structure to the AX2 generic formula.

Ca(OH)2 hybridization

Orbitals are combined during the hybridization process to produce new orbitals with essentially differing energies. Let us examine the hybridization of Ca(OH)2.

Ca(OH)2 exhibits sp hybridization because of the Ca atom’s Steric number of 2. The VSEPR theory predicts that this causes a molecule with the steric number 2 to undergo sp hybridization. There, the atomic orbitals of the object are rearranged.

  • However, there is an ion OH- present, and this will cause sp3 hybridization.
  • Therefore, when these two hybridizations are combined, sp2 hybridization should result.
  • To create a new, equally energetic sp hybrid orbital, the one s and one p orbitals of the Ca atom overlap and merge.

Is Ca(OH)2 solid?

Solid are closely packed and have a definite mass and volume, solids have a specific shape. Let us discuss whether or not Ca(OH)2 is solid.

Ca(OH)2 is a solid form of an inorganic chemical. It has a powdery, white look. However, the crystalline form of Ca(OH)2 appears colourless.

Why is Ca(OH)2 solid?

Ca(OH)2 is solid because of a few rigorous conditions; 

  • The amount of CaO used, 
  • The length of time the crystals grew, and
  • The degree of hydration.
  • Crystals of the portlandite mineral will result from this. 

Is Ca(OH)2 soluble in water?

A chemical compound’s solubility refers to how easily it can dissolve in a solvent like water. Let us examine Ca(OH)2 solubility in water.

Ca(OH)2 is generally less soluble in water. As the temperature rises, Ca(OH)2 becomes less soluble in water due to a thermodynamic fact and follows Le Chatelier’s principle:

Ca(OH)2 = Ca2++ 2OH+Q( heat released).

Why Ca(OH)2 is not soluble in cold water?

Ca(OH)2 is not soluble in cold water because it dissolves in water through an exothermic reaction. The lattice energy of hydroxide salts has decreased, which accounts for the reduced solubility.

  • Temperature affects the solubility of Ca(OH)2 as follows:
  • Temperature rises its solubility declines ie; 
  • Solubility of Ca(OH)2 is 1.73 g/l at 20°C. 
  • Solubility of Ca(OH)2 is 1.89 g/l at 0°C.

Is Ca(OH)2 polar or nonpolar?

Understanding a molecule’s polarity requires knowledge of its electronegativity, electron dispersion, and dipole moment. Let us discuss the polar or nonpolar nature of Ca(OH)2.

Calcium hydroxide is a polar compound. Due to the lower electronegativity of Ca, which exists as a Ca2+ dipole and the higher electronegativity of the O atom in the OH radical, which acts as an OH dipole.

Why Ca(OH)2 is polar?

Ca(OH)2 is a polar compound because only molecules with hydrogen atoms directly bound to highly electronegative atoms can form hydrogen bonds. The formation of an opposing dipole makes it ionic and causes polar character.

Is Ca(OH)2 molecular compound?

The category of pure substance includes substances that are chemical compounds. Let us find out whether Ca(OH)2 is molecular or not.

Ca(OH)2 is not a molecular compound because it is an inorganic salt. Ca=[Ar]4s2 and O=[He]2s22p4 are their outer valence electronic configurations. This shows that molecules are made by the transfer of electrons from Ca2+ to OH ions. 

Is Ca(OH)2 acid or base?

Acids and bases are chemicals or species, respectively, that either give or accept protons. Below is a brief discussion of Ca(OH)2 basic or acidic properties.

Calcium hydroxide is a strong base with a high pH. Ca possesses metallic properties, which means it has a greater tendency to lose electrons. This is because it is a metal hydroxide, which is often basic. A pH of 10 to 11 is considered to be basic.

Why Ca(OH)2 is basic?

Ca(OH)2 is basic because as the atom gets larger, ionization of the atom decreases and the atom becomes more basic. According to the Arrhenius theory, the molecule that produces OH- ions in solution is either alkaline or basic.

Is Ca(OH)2 electrolyte?

Electrolytes are substances that conduct electricity when they are dissolved in water or other chemicals. Let us check to see if Ca(OH)2 is an electrolyte.

Calcium hydroxide is a strong electrolyte. Since it produces OH ions on electrolytic dissociation. Strong bases are always strong electrolytes due to the production of ions in solution. The chemical equation below represents the formed ions.

Ca(OH)2 → Ca2+ + 2 OH

Is Ca(OH)2 salt?

Salt is a chemical compound made up of cations and anions, although it has no net charge. Let us determine whether Ca(OH)2 is salt or not.

Ca(OH)2 is a salt because it is frequently produced by reactions between H2O and CaO. The reaction is as follows: 

CaO + H2O → Ca(OH)2

When combined with water, only a small percentage of it dissolves to make limewater; the remainder remains as a suspension known as milk of lime.

Is Ca(OH)2 ionic or covalent?

Ionic compound with a strong dipole moment as a result of the opposite dipoles that are created on it. Let us find out whether Ca(OH)2 is ionic or covalent.

Ca(OH)2 is an ionic compound. This is because when Ca(OH)2 dissolves in water or when it is molten, it disintegrates to produce Ca2+ and OH ions. This is a crucial aspect of an ionic compound.

  • In either a molten or watery condition, it conducts electricity. 
  • Molten states contain Ca2+ and OH ions,
  • Ca(OH)2 is soluble in polar solvents like water, methanol, etc., just as ionic compounds do.


Ca(OH)2 is an inorganic compound that exists in solid form. It seems colourless and powdery white in appearance.The Lewis structure of Ca(OH)2 contains a total of 2 + 14 = 16 valence electrons. Due to the presence of the ion OH, sp3 hybridization will also occur.

Monika Saini

Hi....I am Monika. I have done Masters in Chemistry. I am a Subject Matter Expert in Chemistry. I would say that I am a very passionate writer. The main goal of my writing is to present new perspectives. I want to discover new things that I can apply to my surroundings. Let's connect through LinkedIn-

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