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Magnesium hydroxide Lewis Structure

Magnesium hydroxide Lewis structure (H2MgO2). O–H single bond. It shows an ionic lattice with no discrete molecular geometry, sp3 hybridization on O. Count 16 valence electrons and a tetrahedral electron-domain arrangement. Polarity: Polar. Abigail3 MIN READSeptember 30, 2026

Magnesium hydroxide Lewis Structure: H2MgO2 Lewis Structure, see text Geometry, sp3 Hybridization & Polarity

Magnesium hydroxide Lewis structure Cover

Magnesium hydroxide Key Facts

The Magnesium hydroxide Lewis structure is O–H single bond; the central O has 4 electron domains (3 lone pairs), giving a tetrahedral electron-domain arrangement and a see text molecular geometry with a — bond angle. O is best described as sp3-hybridized, and Magnesium hydroxide is polar because the see text shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Magnesium hydroxide Lewis Structure Figure 1: Lewis Structure of Magnesium hydroxide (H2MgO2)
Chemical Formula H2MgO2
CAS Number 1309-42-8
Total Valence Electrons 16
Lewis Structure O–H single bond
Electron-Domain Geometry tetrahedral
Molecular Geometry see text
Hybridization Model sp3 (central O)
Bond Angle —
Polarity Polar molecule
PubChem (CID 73981) and NIST list Magnesium hydroxide as H 2MgO 2 with CAS 1309-42-8; molecular weight ≈ 58.320 g/mol. View CAS 1309-42-8 dictionary details on Guidechem →

Applications of Magnesium hydroxide (CAS 1309-42-8)

Magnesium hydroxide is encountered as a reagent, intermediate or specialty chemical in inorganic, organometallic and materials synthesis. Confirm grade, purity and supplier documentation (SDS) before specifying for a process.

Reagent / Intermediate Used in synthesis and formulation where the substance's reactivity is required.
Specialty Chemical Specified by grade for the intended process or research use.
Sourcing Verify purity, package and regional availability via the CAS identifier.
Procurement Note "Magnesium hydroxide" 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 1309-42-8 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Magnesium hydroxide Lewis structure we first count the total valence electrons. H2MgO2 contains 2×1 (H) + 2 (Mg) + 2×6 (O); the net charge of 0 gives a total of 16 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 = 2×1 (H) + 2 (Mg) + 2×6 (O) = 16 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: O–H single bond; 3 lone pairs on O.

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

O–H
O: 3 lone pairs, 1 bonding domain
1 bonding domains + 3 lone pairs = 4 electron domains
Octet Rule: Why O Has Eight Electrons O forms 1 bond(s) and retains 6 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 O arrange to minimize mutual repulsion, giving an tetrahedral 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 see text; the O bond angle is set to — 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 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 sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (1 bonding + 3 lone pair).

Formal-charge check

Formal charge on central O = V − N − ½B = 6 − 6 − ½×2 = 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: sp3 is a compact model for the 4 electron-domain directions around O; full quantum-chemical treatments use molecular orbitals.

Is Magnesium hydroxide Polar or Nonpolar?

Magnesium hydroxide is polar. The see text 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 Magnesium hydroxide the see text 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
Magnesium hydroxide H2MgO2 O 4 see text 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 16 valence electrons of H2MgO2, draw the Lewis structure and confirm the central O atom is sp3-hybridized with see text 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 Magnesium hydroxide (CAS 1309-42-8)? Browse Supplier on Guidechem →

FAQs

Is H2MgO2 polar or nonpolar?

Magnesium hydroxide is polar. Its see text geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Magnesium hydroxide?

O–H single bond; 3 lone pairs on O. It uses all 16 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in Magnesium hydroxide?

The O angle is about —. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.

What is the hybridization of O in Magnesium hydroxide?

The conventional model is sp3. Magnesium hydroxide has 4 electron domains around the central O.

What is the CAS number of Magnesium hydroxide?

The CAS number is 1309-42-8. PubChem (CID 73981) and NIST identify this with H2MgO2; use it to locate suppliers and database records.

References

  1. PubChem CID 73981, Magnesium hydroxide. Molecular formula, CAS number, molecular weight and chemical identity.
  2. NIST Chemistry WebBook, SRD 69, Magnesium hydroxide. Formula, CAS Registry Number and thermochemical / spectroscopic data.
  3. IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
  4. Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
  5. Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for Magnesium hydroxide (CAS 1309-42-8).

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 1309-42-8 identifies the substance, not a universal purity specification.

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