Calcium oxide Lewis Structure

Calcium oxide Lewis Structure: CaO Lewis Structure, linear (diatomic) Geometry, sp2 Hybridization & Polarity

Calcium oxide Key Facts

The Calcium oxide Lewis structure is a linear diatomic with a polar bond between its two atoms; because the two atoms differ in electronegativity, Calcium oxide is polar.

Figure 1: Lewis Structure of Calcium oxide (CaO)

Chemical Formula	CaO
CAS Number	1305-78-8
Total Valence Electrons	8
Lewis Structure	linear diatomic molecule with one double bond
Electron-Domain Geometry	linear
Molecular Geometry	linear (diatomic)
Hybridization Model	sp2
Bond Angle	180°
Polarity	Polar molecule

PubChem (CID 14778) and NIST list Calcium oxide as CaO with CAS 1305-78-8; molecular weight ≈ 56.08 g/mol. View CAS 1305-78-8 dictionary details on Guidechem →

Applications of Calcium oxide (CAS 1305-78-8)

This organic compound is used as a solvent, intermediate or specialty reagent in fine-chemical, pharmaceutical and materials synthesis; specify grade and impurity profile when sourcing.

Solvent / Reagent Medium for reactions, extraction or formulation.

Intermediate Building block for downstream derivatives.

Specialty Use Targeted role in pharma/fragrance/materials.

Procurement Note "Calcium oxide" is supplied in multiple commercial grades and package sizes. Specify purity, grade, moisture/impurity limits, package (cylinder, drum or bulk) and intended process, and use CAS 1305-78-8 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Calcium oxide Lewis structure we first count the total valence electrons. CaO contains 2 (Ca) + 6 (O); the net charge of 0 gives a total of 8 valence electrons to place.

The central atom is O. It is the least electronegative atom capable of forming multiple bonds and is surrounded by the more electronegative terminal atom(s); hydrogen, when present, always occupies a terminal position. Electronegativity considerations place the electron density toward the terminal atom(s).

Valence-electron count

Total valence electrons = 2 (Ca) + 6 (O) = 8 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place O at the center and connect each surrounding atom with a single bond, complete octets on the terminal atoms, and place any remaining electrons on the central atom. The resulting electron distribution is: linear diatomic molecule with one double bond; 2 lone pair(s) on O.

Counting bonding and nonbonding electrons around O therefore satisfies the octet/expanded-octet requirement for the drawn structure.

O–Ca

O: 2 lone pairs, 1 bonding domain

1 bonding domains + 2 lone pairs = 3 electron domains

Octet & Diradical Note In a simple Lewis drawing each atom of this homonuclear diatomic carries lone pairs; species such as O₂ are more accurately described by molecular-orbital theory (paramagnetism arises from unpaired electrons in π* orbitals).

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 3 electron domains around O arrange to minimize mutual repulsion, giving an linear electron-domain geometry.

Because 2 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is linear (diatomic); the O bond angle is set to 180° rather than the ideal value for the electron-domain geometry.

Repulsion hierarchy

A useful VSEPR approximation is: lone pair–lone pair repulsion > lone pair–bonding pair repulsion > bonding pair–bonding pair repulsion. With 2 lone pair(s) on O, the lone-pair domains occupy positions that minimize overall repulsion while pushing the bonding domains (and therefore the bonded atoms) closer together.

Hybridization & Formal Charge

In the conventional localized-bond model, O uses sp2 hybrid orbitals to form the 3 equivalent electron-domain directions (1 bonding + 2 lone pair).

Formal-charge check

Formal charge on central O = V − N − ½B = 6 − 4 − ½×4 = 0. The preferred Lewis structure carries zero formal charge on the central atom (and on the terminals), so it is the dominant contributor.

Modeling Note Modeling Note: sp2 is a compact model for the 3 electron-domain directions around O; full quantum-chemical treatments use molecular orbitals.

Is Calcium oxide Polar or Nonpolar?

Calcium oxide is polar. The linear (diatomic) shape prevents cancellation of the bond dipoles. The bond dipoles do not cancel, leaving a net molecular dipole, which strongly influences solvation behavior and intermolecular interactions.

Expert Quote — Structural Chemistry Perspective

The decisive structural fact is not simply that the individual bonds are polar; it is whether molecular symmetry allows their vector sum to vanish. In Calcium oxide the linear (diatomic) arrangement prevents cancellation, so a permanent dipole remains.

Interpretation consistent with standard VSEPR / molecular-geometry references.

This polarity profile underpins its behavior as a solvent, reactant or process intermediate; when sourcing, specify grade and container compatibility.

Structural Comparison Table

Species	Formula	Central Atom	Electron Domains	Molecular Geometry	Polarity
Calcium oxide	CaO	O	3	linear (diatomic)	Polar
Water	H₂O	O	4	bent	Polar
Hydrogen peroxide	H₂O₂	O	4	bent	Polar
Ozone	O₃	O	3	bent	Polar
Hydronium	H₃O	O	4	trigonal pyramidal	Polar
Hypochlorite	ClO	O	4	linear (diatomic)	Polar

Practice question Starting from the 8 valence electrons of CaO, draw the Lewis structure and confirm the central O atom is sp2-hybridized with linear (diatomic) geometry. What happens to the bond angle if one terminal atom is replaced by a more electronegative substituent?

Looking for industrial bulk or specified-grade supplies of Calcium oxide (CAS 1305-78-8)? Browse Supplier on Guidechem →

FAQs

Is CaO polar or nonpolar?

Calcium oxide is polar. Its linear (diatomic) geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Calcium oxide?

linear diatomic molecule with one double bond; 2 lone pair(s) on O. It uses all 8 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in Calcium oxide?

The O angle is about 180°. Lone-pair repulsion compresses the angle from the ideal linear value.

What is the hybridization of O in Calcium oxide?

The conventional model is sp2. Calcium oxide has 3 electron domains around the central O.

What is the CAS number of Calcium oxide?

The CAS number is 1305-78-8. PubChem (CID 14778) and NIST identify this with CaO; use it to locate suppliers and database records.

References

PubChem CID 14778, Calcium oxide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Calcium oxide. Formula, CAS Registry Number and thermochemical / spectroscopic data.
IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for Calcium oxide (CAS 1305-78-8).

Technical scope: Lewis structures, VSEPR and hybridization are model-based descriptions for chemical communication and structure prediction; actual molecular electronic structure is more accurately represented by molecular-orbital and quantum-chemical methods. Commercial grades vary substantially by supplier and intended use; CAS 1305-78-8 identifies the substance, not a universal purity specification.

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Calcium oxide Lewis Structure