Potassium phosphide Lewis Structure

Potassium phosphide Lewis Structure: H₂K₃P+₂ Lewis Structure, bent Geometry, sp3 Hybridization & Polarity

Potassium phosphide Key Facts

The Potassium phosphide Lewis structure is 2 P–H single bond; the central P has 4 electron domains (2 lone pairs), giving a tetrahedral electron-domain arrangement and a bent molecular geometry with a ≈104.5° bond angle. P is best described as sp3-hybridized, and Potassium phosphide is polar because the bent shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Potassium phosphide (H₂K₃P+₂)

Chemical Formula	H₂K₃P+₂
CAS Number	20770-41-6
Net Charge	+2
Total Valence Electrons	8
Lewis Structure	2 P–H single bond
Electron-Domain Geometry	tetrahedral
Molecular Geometry	bent
Hybridization Model	sp3 (central P)
Bond Angle	≈104.5°
Polarity	Polar molecule

PubChem (CID 62745) and NIST list Potassium phosphide as H ₂K ₃P+ ₂ with CAS 20770-41-6; molecular weight ≈ 150.285 g/mol. View CAS 20770-41-6 dictionary details on Guidechem →

Applications of Potassium phosphide (CAS 20770-41-6)

In aqueous and process chemistry, H₂K₃P+₂ exists as the cation Potassium phosphide ion. It is encountered as a counterion and a controlled source of P in salts, buffers, electrochemistry and analytical protocols, and as a reactant in syntheses that require a defined equivalent of P-containing material.

Ion Source / Counterion Supplied as salts and solutions; specify hydration, counter-cation and concentration.

Analytical & Electrochemical Used in titrations, plating baths and ionic-strength control where the ion is the active species.

Synthesis Reagent A controlled source of P in precipitation, complexation and redox procedures.

Procurement Note "Potassium phosphide" 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 20770-41-6 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Potassium phosphide Lewis structure we first count the total valence electrons. H₂K₃P+₂ contains 2×1 (H) + 3×1 (K) + 5 (P) + 2 (net cation); the net charge of +2 gives a total of 8 valence electrons to place.

The central atom is P. 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 = 2×1 (H) + 3×1 (K) + 5 (P) + 2 (net cation) = 8 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place P 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: 2 P–H single bond; 2 lone pairs on P.

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

P–H ×2

P: 2 lone pairs, 2 bonding domains

2 bonding domains + 2 lone pairs = 4 electron domains

Octet Rule: Why P Has Eight Electrons P forms 2 bond(s) and retains 4 nonbonding electron(s), reaching an octet. No expanded octet is required for this second-row (or octet-satisfying) central atom.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 4 electron domains around P arrange to minimize mutual repulsion, giving an tetrahedral 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 bent; the P bond angle is set to ≈104.5° 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 P, 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, P uses sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (2 bonding + 2 lone pair).

Formal-charge check

Formal charge on central P = V − N − ½B = 5 − 4 − ½×4 = 1. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp3 is a compact model for the 4 electron-domain directions around P; full quantum-chemical treatments use molecular orbitals.

Is Potassium phosphide Polar or Nonpolar?

Potassium phosphide is polar. The bent 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 Potassium phosphide the bent 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
Potassium phosphide	H₂K₃P+₂	P	4	bent	Polar
Phosphine	H₃P	P	4	trigonal pyramidal	Polar
Phosphorus trichloride	Cl₃P	P	4	trigonal pyramidal	Polar
Phosphorus pentachloride	Cl₅P	P	5	trigonal bipyramidal	Nonpolar
Phosphorus trifluoride	F₃P	P	4	trigonal pyramidal	Polar
Phosphorus pentafluoride	F₅P	P	5	trigonal bipyramidal	Nonpolar

Practice question Starting from the 8 valence electrons of H₂K₃P+₂, draw the Lewis structure and confirm the central P atom is sp3-hybridized with bent 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 Potassium phosphide (CAS 20770-41-6)? Browse Supplier on Guidechem →

FAQs

Is H₂K₃P+₂ polar or nonpolar?

Potassium phosphide is polar. Its bent geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Potassium phosphide?

2 P–H single bond; 2 lone pairs on P. 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 Potassium phosphide?

The P angle is about ≈104.5°. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.

What is the hybridization of P in Potassium phosphide?

The conventional model is sp3. Potassium phosphide has 4 electron domains around the central P.

What is the CAS number of Potassium phosphide?

The CAS number is 20770-41-6. PubChem (CID 62745) and NIST identify this with H₂K₃P+₂; use it to locate suppliers and database records.

References

PubChem CID 62745, Potassium phosphide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Potassium phosphide. 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 Potassium phosphide (CAS 20770-41-6).

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 20770-41-6 identifies the substance, not a universal purity specification.

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Potassium phosphide Lewis Structure

Potassium phosphide Lewis Structure