CaCO3 Lewis Structure & Characteristics: 15 Complete Facts

Calcium carbonate commonly called as lime stone. Let us discuss about CaCO3 lewis structure and 15 complete facts.

CaCO3 or Calcium carbonate is a carbonic salt of calcium. Calcium carbonate’s molar mass is 100.86 g/mol, with no odour. It is a white crystalline powder which easily decomposes on heating. The melting point of calcium carbonate is 13390C.

Calcium carbonate is used as an antacid, calcium supplement.  Let us look into some interesting facts about CaCO3.

How to Draw CaCO3 Lewis Structure?

Lewis structure representation can be used to calculate the formal charge of atoms present in a molecule. Let us see the steps in drawing Lewis structure of CaCO3.

Calculating the total valence electrons

Calcium with two valence electrons and carbon has four electrons, oxygen with six valence electrons. So in total 2+4+3*6 = 24 electrons.

Drawing the skeletal structure

Carbon being the least electronegative atom is considered as the central atom attached with three oxygen atoms. This contributes the lewis structure of carbonate ion.

Making bonds and distribution of electrons

Three bonds are made between the oxygen and carbon. In order to satisfy carbon’s valency one additional bond is made between one of the oxygen and carbon. The carbonate ion with negative charge then combines with Ca ion to make CaCO3.

caco3 lewis structure
Lewis Structure of CaCO3

CaCO3 Lewis Structure Resonance

Resonance can result more than one structure to a molecule with different energy. Let us look into CaCO3 lewis structure resonance.

CaCO3 lewis structure has resonance due to the presence of carbonate ion. The lone pairs present in oxygen involves in delocalisation to result resonance. Due to this process it can have three resonating structures.

Resonance in CaCO3

CaCO3 Lewis Structure Shape

Shape of a molecule mainly deals with bond length and bond angle between the atoms present in the molecule. Let us see the shape of CaCO3.

The shape of CaCO3 lewis structure is triagonal.Actually carbonate ion in CaCO3 is triagonal in shape. In triagonal structure all the oxygens are joined with the carbon atom in a triagonal manner. CaCO3 has stable hexagonal form, denser with orthorhombic form.

CaCO3 Lewis Structure Formal Charge

The formal charge of all atoms in a molecule can be negative, positive and zero. Let us calculate the formal charge of CaCO3.

The formal charge of CaCO3 lewis structure is not zero. It is negative and positive values including zero.

The equation for finding formal charge is

  • Formal charge= valence electrons – Non bonding electrons – No of bonds
  • Formal charge of carbon = 4-0-4 = 0
  • Formal charge of oxygen double bonded with carbon = 6-4-2 = 0
  • Formal charge of oxygens single bonded with carbon =6-6-1 = -1
  • Formal charge of calcium = 2-0-1=1

CaCO3 Lewis Structure Angle

Bond angle is made between atoms when they arrange themselves in a very stable manner to reduce repulsion in between them. Let us know the bond angle of CaCO3.
The bond angle of CaCO3 lewis structure is 1200. Since it has a triagonal shape the entire angle are 1200.

CaCO3 Lewis Structure Octet Rule

Octet rule explains about the stability of an atom after bond making. Let us look whether CaCO3 obeys octet or not.

CaCO3 lewis structure obeys octet rule. Carbon and oxygen has eight electrons in their valence shell after bond making. Calcium loses its two electrons to make its octet satisfied. So all the atoms in caco3 satisfies octet rule with eight electrons in valence shell.

CaCO3 Lewis Structure Lone Pairs

Lone pairs usually didn’t participate in reaction but has a prominent role in shape and angle determination of a compound. Let us look the number of lone pairs in CaCO3.

CaCO3 Lewis structure has eight lone pairs. All the lone pairs are seen in oxygen atom. The two oxygen atoms which single bonded with carbon has three pairs and one double bonded oxygen has two. So total eight lone pairs or 16 non-bonding electrons.

CaCO3 Valence Electrons

Valence electrons has a crucial role in drawing the lewis structure of any molecule. Let us count the valence electrons in CaCO3.

The valence electrons in CaCO3 Lewis structure is 24. Calcium with two valence electrons, carbon has four and oxygen with six. So in total 2+4+6×3=24.

CaCO3 Hybridization

The new orbitals formed as a result of hybridisation projects outwards for enhancing its overlapping ability. Let us know the hybridisation of CaCO3.

The hybridisation is CaCO3 Lewis structure is sp2. In this the one s and two p orbitals of carbon overlaps with p orbital of oxygen to undergo sp2 hybridization in CaCO3. It has triagonal planar shape with 1200 bond angle.

Is CaCO3 Solid?

Solids are three dimensional shapes with height, width and length. Let us see whether CaCO3 is solid or not.

CaCO3 is a solid which is white in colour. It is a fine powder like nature with a chalky taste. It has a three dimensional structure like solid with well-arranged in a regular pattern.

Is CaCO3 Soluble in Water?

Temperature is an important factor that can alter the solubility of any solute in solvent. Let us see the solubility of CaCO3 in water.

CaCO3 is not very much soluble in water. Even though water and CaCO3 is ionic compound they are found to be poorly soluble in water.

Why CaCO3 Not Soluble in Water?

CaCO3 is not much soluble in water because of the strong electrostatic force of attraction between Ca2+ and CO32- ion present here. The solubility product of caco3 is found to be 3.3 * 10-9  .

Is CaCO3 a Polar or Non-polar?

Polar compounds are separated by two opposite charges with very small distance. Let us see CaCO3 is polar or not.

CaCO3 is a polar compound. CaCO3 is formed by the electrostatic force of attraction between two opposite charges. So the compound is polar. The electronegativity difference between the atoms also shows they are polar in nature.

Is CaCO3 Acid or Base?

Acids are electron acceptors and bases are electron donors. Let us know CaCO3 is acid or base.

CaCO3 is actually a salt but it has slightly basic character. It is formed as a result of neutralisation reaction so it’s a salt.

Why CaCO3 is Basic ?

CaCO3 is basic because it is formed from strong base called calcium hydroxide and weak acid carbonic acid. When a strong base reacts with weak acid the salt formed will be basic in character. So CaCO3 is basic and used as an antacid to reduce acidic effect.

Is CaCO3 Electrolyte ?

Electrolyte has the ability to dissociate in water to conduct electricity. Let us see CaCO3 is electrolyte or not.

CaCO3 is not a good electrolyte. It is because of its poor solubility in water. A good electrolyte easily dissolve in water to dissociate into ions but CaCO3 poorly dissociate to corresponding ions. It is not a good or strong electrolyte.

Is CaCO3 Salt?

Salt is a neutral substance with sometimes acidic or basic character. Let us know CaCO3 is salt or not.

CaCO3 is a salt. It is a salt with basic nature.CaCO3 is formed by the reaction between strong base like calcium hydroxide and weak acid called carbonic acid.

An acid and base always reacts to give salt and water. Here also they both react to give the neutral substance called CaCO3 with water as by product.

Is CaCO3 Ionic or Covalent?

Ionic compound are mainly formed by the combination of metals and non-metals. Let us look whether CaCO3 is ionic or covalent.

CaCO3 is an ionic compound. In the case of CaCO3 carbonate is negative and Ca ion is positive. The force of attraction between them holds them together in a strong way. So in CaCO3 bond is formed between calcium metal and carbonate ion which comprises non-metal.


CaCO3 or calcium carbonate is used in refining of sugar, scrubbing agents and in construction works. This article briefly explains that CaCO3 has sp2 hybridisation with 24 valence electrons. Its lewis structure is drawn here in this article with all details.

Aparna Dev

Hi... I am Aparna Dev, a chemistry Postgraduate with a good understanding of chemistry concepts. I am working in Kerala Minerals and Metals Limited Kollam with experience in the development of electrocatalysts as a part of post graduate thesis. Let's connect through LinkedIn-

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