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Chemical substance record

Silicon

7440-21-3Si28.086 g/mol
ElementChEBI source record

Silicon is indexed in ChEBI under CHEBI:27573, with the reported formula Si. Use the source record and structural identifiers below to confirm the material you need. — ChEBI

Safety references

Safety documents & references

2 indexed references
US · NIOSH

Occupational chemical safety guide

Silicon

Read official guide
JP · NITE

Government GHS classification

21A3549 · FY2009

View classification

Find a product-specific SDS

Safety guides and government classification records are not a manufacturer’s SDS. Match supplier, product number, concentration, physical form, region and revision before using a document.

Identity & molecular properties

Source-linked values
CAS number7440-21-3ChEBI ↗
Molecular formulaSiChEBI ↗
Molar mass28.086 g/molChEBI ↗
Monoisotopic mass27.97693 DaChEBI ↗
Formal charge0ChEBI ↗
ChEBI identifierCHEBI:27573ChEBI ↗

Cross-source molecular data

PubChem
Molar mass28.085 g/molPubChem ↗
Exact mass27.976926534 DaPubChem ↗

PubChem computed values are shown separately from the ChEBI record. An exact InChIKey match was used to connect the records. Molecular descriptors do not describe a supplied product’s purity, particle size or performance.

Names & structural identifiers

Copy any identifier
silicon atom
silicon
XUIMIQQOPSSXEZ-UHFFFAOYSA-N
[Si]
InChI=1S/Si

Names & synonyms

silicon

Names are supplied by ChEBI. Trade names and related synonyms may describe a broader product context.

Classification & relationships

ChEBI ontology

Safety classification · Japan

NITE / Japanese government
Japan · FY2009 source classification
Silicon (powder, amorphous) · 21A3549
EndpointReported classification
Flammable solidsCategory 2
Serious eye damage/eye irritationCategory 2B

Selected source-reported endpoints. Other endpoints, rationales and conditions remain in the original classification. Missing or unlisted information does not mean non-hazardous. This is not a global classification or transport decision.

Read the original NITE classification

Mass ↔ amount of substance

Calculated from sourced mass
Equivalent amount
0.0356049 mol

Uses 28.086 g/mol from ChEBI. Assumes the substance described by this record; no purity or concentration correction is applied.

Elemental composition

Theoretical mass fractions
Si
Silicon · 1 atom
100.00%

Calculated theoretical mass fractions from the reported formula and PubChem periodic-table atomic masses. These are not assay or purity results.

Research & patent references

Selected source associations

Explore literature using this exact identifier.

Sources & record history

Checked 27 Sep 2026
EMBL-EBI ChEBI · CHEBI:27573

Release 255, 9 September 2026. ChEBI three-star (manually annotated) source entry. View original record ↗ · CC BY 4.0

NCBI PubChem · CID 5461123 · retrieved 2026-09-27

PubCAS formats source data, connects references and computes explicitly labelled conversions. CAS cross-references are supplied by ChEBI; they do not constitute CAS verification or endorsement.