Calcium sulfide Lewis Structure

Calcium sulfide Lewis Structure: CaS Lewis Structure, linear (diatomic) Geometry, sp3d Hybridization & Polarity

Calcium sulfide Key Facts

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

Figure 1: Lewis Structure of Calcium sulfide (CaS)

Chemical Formula	CaS
CAS Number	20548-54-3
Total Valence Electrons	8
Lewis Structure	linear diatomic molecule with one single bond
Electron-Domain Geometry	linear
Molecular Geometry	linear (diatomic)
Hybridization Model	sp3d
Bond Angle	180°
Polarity	Polar molecule

PubChem (CID 10197613) and NIST list Calcium sulfide as CaS with CAS 20548-54-3; molecular weight ≈ 72.15 g/mol. View CAS 20548-54-3 dictionary details on Guidechem →

Applications of Calcium sulfide (CAS 20548-54-3)

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 sulfide" 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 20548-54-3 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 sulfide Lewis structure we first count the total valence electrons. CaS contains 2 (Ca) + 6 (S); the net charge of 0 gives a total of 8 valence electrons to place.

The central atom is S. 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 (S) = 8 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place S 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 single bond; 3 lone pair(s) on S.

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

S–Ca

S: 3 lone pairs, 1 bonding domain

1 bonding domains + 3 lone pairs = 5 electron domains

Expanded Octet: d-Orbital Participation Central S belongs to period 3 or below, so it can accommodate more than eight electrons: low-lying d orbitals become available and the linear (diatomic) arrangement with 5 domains reflects this expanded valence shell. The octet rule alone does not apply to such hypervalent species.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 5 electron domains around S arrange to minimize mutual repulsion, giving an linear electron-domain geometry.

Because 3 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is linear (diatomic); the S 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 3 lone pair(s) on S, 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, S uses sp3d hybrid orbitals to form the 5 equivalent electron-domain directions (1 bonding + 3 lone pair).

Formal-charge check

Formal charge on central S = V − N − ½B = 6 − 6 − ½×2 = -1. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp3d / sp3d hybridization is a convenient localized-bond teaching model. Modern quantum-chemical descriptions of hypervalent Calcium sulfide use molecular orbitals and do not require populated d orbitals as the primary bonding picture.

Is Calcium sulfide Polar or Nonpolar?

Calcium sulfide 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 sulfide 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 sulfide	CaS	S	5	linear (diatomic)	Polar
Sulfur dioxide	SO₂	S	3	bent	Polar
Sulfur trioxide	O₃S	S	3	trigonal planar	Nonpolar
Sulfur hexafluoride	F₆S	S	6	octahedral	Nonpolar
Sulfur tetrafluoride	F₄S	S	5	seesaw	Polar
Sulfate	O₄S	S	4	tetrahedral	Nonpolar

Practice question Starting from the 8 valence electrons of CaS, draw the Lewis structure and confirm the central S atom is sp3d-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 sulfide (CAS 20548-54-3)? Browse Supplier on Guidechem →

FAQs

Is CaS polar or nonpolar?

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

What is the Lewis structure of Calcium sulfide?

linear diatomic molecule with one single bond; 3 lone pair(s) on S. It uses all 8 valence electrons and the preferred structure carries a formal charge of -1 on the central atom.

What is the bond angle in Calcium sulfide?

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

What is the hybridization of S in Calcium sulfide?

The conventional model is sp3d. Calcium sulfide has 5 electron domains around the central S.

What is the CAS number of Calcium sulfide?

The CAS number is 20548-54-3. PubChem (CID 10197613) and NIST identify this with CaS; use it to locate suppliers and database records.

References

PubChem CID 10197613, Calcium sulfide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Calcium sulfide. 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 sulfide (CAS 20548-54-3).

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 20548-54-3 identifies the substance, not a universal purity specification.

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Calcium sulfide Lewis Structure