Element / isotope identity
Atomic number, isotope identity and discovery evidence are experimentally/evaluatively grounded.
Electron configuration
Very-heavy-element configurations are theory/evaluation-led; ordinary elements use evaluated ground-state references.
Bulk material structure
Historical electron-diffraction lines from eleven tiny metal samples were indexed as FCC (reported a about 0.575 nm). Self-irradiation and sample scarcity make this much weaker than ordinary bulk crystallography.
Phase / density data
A reported melting reference is retained, while density, boiling point and other unmeasured bulk values stay unknown.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Einsteinium (Es)
Einsteinium is element 99. This guide connects its periodic-table identity to evidence-aware structure, isotopes, uses, discovery and the search questions learners actually ask.
Einsteinium atomic number, mass, electron configuration and key properties
Einsteinium: quick answers
How many protons, neutrons and electrons does einsteinium have?
Einsteinium’s atomic number is 99, so every einsteinium atom has 99 protons, and a neutral atom also has 99 electrons. Einsteinium has no stable isotopes, so the neutron count depends on the isotope: einsteinium-252, featured on this page, has 153 neutrons.
What is the symbol for einsteinium?
The chemical symbol for einsteinium is Es.
Is einsteinium a solid, liquid or gas at room temperature?
Einsteinium is a solid at room temperature (about 25 °C).
What family (group) is einsteinium in?
Einsteinium is an actinide, in period 7 (the f-block row shown below the main table) of the periodic table.
What is the electron configuration of einsteinium?
The ground-state electron configuration of einsteinium is [Rn] 5f¹¹ 7s².
From atomic number to chemistry
Read these as a chain of causes, not as isolated facts. Each step links to the concept hub if you want the underlying idea explained.
99 protons define einsteinium.
Ground-state/reference configuration frames atomic behavior; heavy-element predictions remain evidence-labelled.
Periodic position organizes trends without replacing element-specific evidence.
The teaching nucleus is one isotope, not the relative atomic mass.
Measured structures are visualized; unknown bulk structures stay unknown.
Einsteinium in its period and family
Einsteinium is element 99 in Period 7. Its f-block/series position provides useful periodic context, but element-specific experimental evidence takes priority over simple trend extrapolation.
Einsteinium Visual Lab
Explore Es across the teaching nucleus, isolated-atom orbitals, a limited-evidence FCC metal teaching cell and temperature/evidence views, then connect those models to uses, isotopes, search-led questions and source-backed context.
Every mark points to one exact feature
The numbered markers explain the same information system used throughout Element Lookup. Unknown or predicted fields remain visibly labelled rather than being replaced with guesses.
Einsteinium in one minute
Atomic number 99 means every einsteinium nucleus has 99 protons.
The ground-state/reference electron configuration is [Rn] 5f¹¹ 7s².
The representative teaching isotope is ²⁵²Es.
Historical electron-diffraction work indexed eleven tiny einsteinium-metal samples as face-centred cubic (FCC), but self-irradiation and sample scarcity strongly limit the evidence.
Material structure status: FCC supported by limited small-sample electron-diffraction evidence; not an ordinary macroscopic crystal measurement.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 29 · 8 · 2 electrons
Displayed orbitals are isolated-atom, nonrelativistic teaching probability models. They are not bulk-band structures, bonding orbitals or direct measured electron-density maps; relativistic effects become especially important for very heavy elements.
Electron-diffraction lines from eleven tiny einsteinium-metal samples were indexed as face-centred cubic (FCC), with a reported lattice parameter near 0.575 nm. Because intense self-irradiation degraded crystallinity and the available material was minute, Element Lookup labels this as limited small-sample structural evidence rather than an ordinary bulk-crystal measurement.. The viewer is evidence-aware: measured structures are identified as such; unknown bulk structures stay unknown.
Teaching visualization; not a literal finite sample or thermal trajectory.What this model does—and does not—show
Displayed orbitals are isolated-atom, nonrelativistic teaching probability models. They are not bulk-band structures, bonding orbitals or direct measured electron-density maps; relativistic effects become especially important for very heavy elements.
Where do I meet einsteinium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Scientific research only
This context uses Einsteinium or a einsteinium-containing material; the element and its compounds/isotopes are kept distinct.
Evidence ladder: nucleus → atom-scale chemistry → unknown bulk material
For scarce synthetic heavy elements, different claims have very different evidence strength.
Nuclear identity
Production/decay evidence establishes the element and specific isotopes.
Einsteinium in periodic context
Compare nearby or family-related elements without treating a periodic trend as a substitute for element-specific evidence.
| Atomic number | 98 |
|---|---|
| Context | neighbor / series |
| Atomic number | 99 |
|---|---|
| Context | neighbor / series |
| Atomic number | 100 |
|---|---|
| Context | neighbor / series |
Einsteinium properties: atomic, physical, thermal and chemical
Categories follow the science of this element rather than a fixed decorative template. Each row carries condition/provenance context and an evidence label; unknown values stay unknown.
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Atomic number | 99 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [252] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Rn] 5f¹¹ 7s² | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group Actinide · Period 7 · f-block | Periodic-table placement | Evaluated |
| Electronegativity | Unknown | Source-reviewed; see Sources below | Unknown |
| Reference isotope | ²⁵²Es | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Radioactive synthetic actinide; only tiny quantities have been produced | Source-reviewed; see Sources below | Evaluated |
| Density | Unknown | Source-reviewed; see Sources below | Unknown |
| Material / molecular structure | Face-centred cubic (FCC) · limited electron-diffraction evidence | Electron-diffraction lines from eleven tiny einsteinium-metal samples were indexed as face-centred cubic (FCC), with a reported lattice parameter near 0.575 nm. Because intense self-irradiation degraded crystallinity and the available material was minute, Element Lookup labels this as limited small-sample structural evidence rather than an ordinary bulk-crystal measurement. | Measured |
| Classification | Actinide | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Electron-diffraction lines from eleven tiny einsteinium-metal samples were indexed as face-centred cubic (FCC), with a reported lattice parameter near 0.575 nm. Because intense self-irradiation degraded crystallinity and the available material was minute, Element Lookup labels this as limited small-sample structural evidence rather than an ordinary bulk-crystal measurement. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 1133 K (reported reference) | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | Unknown | Source-reviewed; see Sources below | Unknown |
| Phase-path context | A melting reference of 1133 K (reported reference) is reported for teaching context, while an ordinary boiling point is not established here. The page does not infer a precise gas transition from theory. | Shared phase registry drives the slider, regions and markers. | Evaluated |
| Condition warning | Temperature and pressure define phase behavior; purity/allotropy may matter. | Teaching condition statement | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | +3 | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Es³⁺ | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Einsteinium is element 99 in Period 7. Its f-block/series position provides useful periodic context, but element-specific experimental evidence takes priority over simple trend extrapolation. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²⁵²Es | Reference teaching isotope | Mass number belongs to a specific isotope and is not the same thing as relative atomic mass. | Evaluated |
| Isotope evidence | Element-specific nuclear context | Half-life and decay properties are isotope-specific; the page does not generalize one isotope to all atoms. | Evaluated |
| Teaching nucleus | ²⁵²Es · 99 protons + 153 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic identity and isotope data are established/evaluated. Historical electron diffraction provides limited FCC structural evidence for tiny einsteinium-metal samples (eleven samples; reported a about 0.575 nm), while severe self-irradiation and sample scarcity make the material evidence much weaker than for ordinary bulk metals. Unknown density/boiling/other bulk values remain visibly unknown. | Evidence summary for this guide | Reviewed |
| Structure evidence | Electron-diffraction lines from eleven tiny einsteinium-metal samples were indexed as face-centred cubic (FCC), with a reported lattice parameter near 0.575 nm. Because intense self-irradiation degraded crystallinity and the available material was minute, Element Lookup labels this as limited small-sample structural evidence rather than an ordinary bulk-crystal measurement. | Measured structure, labelled schematic, prediction or explicit unknown as applicable. | Reviewed |
| Map evidence rule | Real pins are reviewed examples; conceptual layers are used when pins would mislead. | Geography Explorer 2.0 | Reviewed |
| Source set | 4 primary/reference links listed below | Open the Sources section for the actual references. | Reviewed |
Is Einsteinium a solid, liquid or gas? State at temperature
A melting reference of 1133 K (reported reference) is reported for teaching context, while an ordinary boiling point is not established here. The page does not infer a precise gas transition from theory.
Where on Earth is Einsteinium found or produced?
Who discovered Einsteinium, and when?
Albert Ghiorso and colleagues identified einsteinium in debris from the first thermonuclear test.
The element name and discovery story are part of the historical record; search-led questions are answered without turning history into scientific evidence for bulk properties.
Current use is described at the level supported by the element’s availability and evidence, with research-only elements kept research-only.
Research production context: high-level, non-operational
The element is produced or isolated only in specialized research/nuclear settings; this page intentionally omits operational synthesis, target, beam, separation, handling and access instructions.
Experimental identity is established from nuclear decay, spectroscopy and/or atom-scale chemistry appropriate to the element.
Any chemical or material inference is labelled by evidence strength; unmeasured bulk properties are not converted into visual facts.
Research use is described conceptually, with isotope-specific claims kept distinct from the element as a whole.
What is einsteinium used for?
Scientific research only
Research-only context; no operational production or handling guidance.
Actinide chemistry and nuclear-structure studies
Research-only context; no operational production or handling guidance.
Einsteinium isotopes and natural abundance
²⁵²Es
Reference teaching isotopeMass number belongs to a specific isotope and is not the same thing as relative atomic mass.
Isotope evidence
Element-specific nuclear contextHalf-life and decay properties are isotope-specific; the page does not generalize one isotope to all atoms.
Five-question Einsteinium check
What is Einsteinium’s atomic number?
Which statement best describes the material evidence for Einsteinium?
What is the safest rule for Einsteinium uses?
Einsteinium questions students commonly ask
Each answer starts with the direct fact, then explains the chemistry, evidence or material context so the result is understandable rather than merely memorized.
What is einsteinium?
Short answer: Einsteinium is chemical element 99, symbol Es, classified here as actinide.
Atomic number 99 means every einsteinium nucleus contains 99 protons. In the periodic table, Einsteinium is classified here as an actinide in Period 7 and Group Actinide. Einsteinium is element 99 in Period 7. Its f-block/series position provides useful periodic context, but element-specific experimental evidence takes priority over simple trend extrapolation.
Key point: Es is element 99; its periodic position and electron structure explain the rest of the page.
What is the atomic number of einsteinium?
Short answer: The atomic number is 99, meaning every einsteinium nucleus has 99 protons.
Atomic number is defined by proton count, so 99 protons are what make an atom einsteinium. A neutral einsteinium atom also has 99 electrons, while isotopes can have different neutron counts without changing the element.
Key point: Atomic number = proton count.
What is the symbol for einsteinium?
Short answer: The chemical symbol is Es.
The symbol Es is the standardized chemical abbreviation for element 99. In a chemical formula, Es identifies einsteinium atoms; a compound containing Es is not automatically the same material as elemental einsteinium.
Key point: Es always identifies element 99.
What is einsteinium used for?
Short answer: Einsteinium has no ordinary commercial use; it is used only in scientific research.
Scientific research only: Research-only context; no operational production or handling guidance. Actinide chemistry and nuclear-structure studies: Research-only context; no operational production or handling guidance. Einsteinium exists only in very small quantities. Unlike later actinides whose pure metal has not been prepared, historical electron-diffraction work did obtain limited FCC structural evidence for tiny einsteinium-metal samples; that evidence is shown with an explicit caveat.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Who discovered einsteinium?
Short answer: Albert Ghiorso and colleagues identified it in 1952 from thermonuclear-test debris.
In 1952, Albert Ghiorso and colleagues identified einsteinium in debris from the first thermonuclear test. The element name and discovery story are part of the historical record; search-led questions are answered without turning history into scientific evidence for bulk properties.
Key point: Discovery credit follows the historical evidence and accepted attribution, not just the earliest claim.
What does einsteinium look like?
Short answer: Einsteinium is described as a radioactive metallic element, but only tiny quantities have existed. Historical electron diffraction supports an FCC metal structure in small samples; that does not amount to a normal macroscopic specimen whose bulk appearance has been directly characterized.
The ordinary elemental-material description used here is: Radioactive synthetic actinide; only tiny quantities have been produced. Einsteinium exists only in very small quantities. Unlike later actinides whose pure metal has not been prepared, historical electron-diffraction work did obtain limited FCC structural evidence for tiny einsteinium-metal samples; that evidence is shown with an explicit caveat.
Key point: Elemental appearance can differ from the colors of its ions, compounds, oxide films or host materials.
What is einsteinium’s crystal structure?
Short answer: Limited electron-diffraction evidence from eleven tiny metal samples was indexed as face-centred cubic (FCC). The result is scientifically useful but should be presented with a strong small-sample/self-irradiation caveat rather than as an ordinary bulk crystal measurement.
Electron-diffraction lines from eleven tiny einsteinium-metal samples were indexed as face-centred cubic (FCC), with a reported lattice parameter near 0.575 nm. Because intense self-irradiation degraded crystallinity and the available material was minute, Element Lookup labels this as limited small-sample structural evidence rather than an ordinary bulk-crystal measurement. The Structure viewer is an evidence-aware teaching model: measured or defensible structures are shown as models, while genuinely unknown bulk structures remain explicitly unknown.
Key point: A teaching lattice is a scientific model, not a photograph of a finite chunk of material.
Scientific sources for Einsteinium
- Royal Society of Chemistry - Einsteinium
- NIST - Atomic Weights and Isotopic Compositions
- IUPAC - Periodic Table of Elements
- OSTI / UCRL-85944 - Chemical properties of einsteinium; metallic-state electron diffraction
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