Element identity
Element 93 and isotope identities are experimental/evaluated.
Solid allotropes
Alpha, beta and gamma metallic structures are established.
Transition temperatures
Slider values are reviewed teaching references with source/condition variation.
Safety boundary
No production, separation, access or criticality instructions.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Neptunium (Np)
Neptunium is element 93, the first transuranium element. Its science combines a long-lived isotope, multiple oxidation states and three solid allotropes—while all nuclear-material discussion stays high-level and non-operational.
Neptunium atomic number, mass, electron configuration and key properties
Neptunium: quick answers
How many protons, neutrons and electrons does neptunium have?
Neptunium’s atomic number is 93, so every neptunium atom has 93 protons, and a neutral atom also has 93 electrons. Neptunium has no stable isotopes, so the neutron count depends on the isotope: neptunium-237, featured on this page, has 144 neutrons.
What is the symbol for neptunium?
The chemical symbol for neptunium is Np.
Is neptunium a solid, liquid or gas at room temperature?
Neptunium is a solid at room temperature (about 25 °C).
What family (group) is neptunium in?
Neptunium 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 neptunium?
The ground-state electron configuration of neptunium is [Rn] 5f⁴ 6d¹ 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.
93 protons define neptunium.
The ground-state configuration provides the starting point for its chemistry.
Periodic position organizes recurring chemistry and trends.
The teaching nucleus is one isotope, not the relative atomic mass.
Phase boundaries are condition-dependent and evidence-labelled.
Neptunium in its period and family
Neptunium follows uranium in the actinide series. Its 5f electrons participate in both complex bonding and multiple oxidation-state chemistry.
Neptunium Visual Lab
Explore ²³⁷Np, f-orbital occupancy, α/β/γ solid structures and a three-transition temperature path, then connect the science to discovery history, oxidation states and environmental/nuclear measurement.
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.
Neptunium in one minute
Atomic number 93 means 93 protons.
Neptunium has no stable isotopes.
²³⁷Np is long-lived, with a half-life of about 2.14 million years.
Neptunium has α, β and γ solid allotropes before melting.
Neptunium chemistry supports several oxidation states, especially +3 through +6.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 22 · 9 · 2 electrons
The 5f/6d/7s orbital models show isolated-atom probability distributions. They do not encode radioactive decay, bulk allotrope energetics or chemical speciation.
Neptunium has three established solid allotropes across temperature: α (orthorhombic), β (tetragonal) and γ (BCC). Viewers are teaching schematics; exact crystallographic coordinates are not implied.. 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
The 5f/6d/7s orbital models show isolated-atom probability distributions. They do not encode radioactive decay, bulk allotrope energetics or chemical speciation.
Where do I meet neptunium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Research
Neptunium is mainly encountered in nuclear and actinide research rather than everyday commercial products.
Three solid allotropes + long-lived ²³⁷Np
Neptunium combines rich metallic phase behavior with nuclear isotope science, which must be kept conceptually separate.
Orthorhombic α-Np
The low-temperature metallic allotrope is orthorhombic.
Uranium, neptunium and plutonium
Compare nearby elements to see which patterns repeat and which properties remain element-specific.
| Z | 92 |
|---|---|
| Stable isotopes | none |
| Z | 93 |
|---|---|
| Reference | 237Np |
| Z | 94 |
|---|---|
| Stable isotopes | none |
Neptunium 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 | 93 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [237] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Rn] 5f⁴ 6d¹ 7s² | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group Actinide · Period 7 · f-block | Periodic-table placement | Evaluated |
| Electronegativity | 1.3 | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ²³⁷Np | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Radioactive silvery metal at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | 20.2 g/cm³ | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Neptunium · α orthorhombic, β tetragonal, γ BCC solid allotropes | Neptunium has three established solid allotropes across temperature: α (orthorhombic), β (tetragonal) and γ (BCC). Viewers are teaching schematics; exact crystallographic coordinates are not implied. | Measured |
| Classification | Actinide | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Neptunium has three established solid allotropes across temperature: α (orthorhombic), β (tetragonal) and γ (BCC). Viewers are teaching schematics; exact crystallographic coordinates are not implied. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 917 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 4175 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | A reviewed heating-path teaching model shows α-Np (orthorhombic) to ~553 K, β-Np (tetragonal) to ~850 K, γ-Np (BCC) to melting near 917 K, then liquid toward the high boiling reference. Transition values vary somewhat among literature/conditions and are treated as teaching references. | 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, +4, +5, +6 (important states) | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Multiple oxidation states, commonly +3 to +6 in compounds | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Neptunium follows uranium in the actinide series. Its 5f electrons participate in both complex bonding and multiple oxidation-state chemistry. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²³⁷Np | Radioactive · t½ ≈2.14 million years | Reference teaching nucleus: 93 protons and 144 neutrons. | Evaluated |
| ²³⁹Np | Short-lived radionuclide | Important in the historical discovery chain and nuclear-decay studies. | Evaluated |
| Neptunium isotope context | No stable isotopes | All neptunium isotopes are radioactive; bracketed relative mass notation reflects this. | Evaluated |
| Teaching nucleus | ²³⁷Np · 93 protons + 144 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic/isotope identity and metallic phase behavior are measured/evaluated. Transition temperatures are teaching references with condition/literature variation. No operational production, separation, criticality or material-access guidance is provided. | Evidence summary for this guide | Reviewed |
| Structure evidence | Neptunium has three established solid allotropes across temperature: α (orthorhombic), β (tetragonal) and γ (BCC). Viewers are teaching schematics; exact crystallographic coordinates are not implied. | 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 | 3 primary/reference links listed below | Open the Sources section for the actual references. | Reviewed |
Is Neptunium a solid, liquid or gas? State at temperature
A reviewed heating-path teaching model shows α-Np (orthorhombic) to ~553 K, β-Np (tetragonal) to ~850 K, γ-Np (BCC) to melting near 917 K, then liquid toward the high boiling reference. Transition values vary somewhat among literature/conditions and are treated as teaching references.
Where on Earth is Neptunium found or produced?
Who discovered Neptunium, and when?
Edwin McMillan and Philip Abelson produced and identified neptunium at Berkeley, the first transuranium element discovered.
Actinide chemistry developed rapidly as researchers investigated artificial heavy elements.
Long-lived ²³⁷Np became important in nuclear chemistry, environmental measurement and waste studies.
Neptunium remains mainly a controlled research and nuclear-materials science topic.
How neptunium enters scientific study: non-operational overview
Neptunium isotopes can arise in irradiated nuclear material and decay chains; this page does not describe production settings.
Research laboratories characterize isotopes, oxidation states and materials using controlled radiological facilities.
Separation, purification and fabrication methods are intentionally excluded from this educational page.
Environmental and nuclear measurements focus on trace detection, isotope identification and long-term behavior.
What is neptunium used for?
Scientific research
Neptunium supports actinide, nuclear-structure, spectroscopy and materials research.
Nuclear measurement
Selected isotopes are relevant to analytical standards, monitoring and nuclear-science studies.
Environmental studies
Long-lived ²³⁷Np is studied in transport and waste-performance contexts.
No ordinary consumer use
Neptunium has no routine bulk consumer application comparable with common structural metals.
Neptunium isotopes and natural abundance
²³⁷Np
Radioactive · t½ ≈2.14 million yearsReference teaching nucleus: 93 protons and 144 neutrons.
²³⁹Np
Short-lived radionuclideImportant in the historical discovery chain and nuclear-decay studies.
Neptunium isotope context
No stable isotopesAll neptunium isotopes are radioactive; bracketed relative mass notation reflects this.
Five-question Neptunium check
Atomic number?
Stable isotopes?
Reference long-lived isotope?
Solid-allotrope sequence on heating?
What kind of guidance is intentionally excluded?
Neptunium 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 neptunium’s atomic number?
Short answer: 93.
Atomic number is defined by proton count, so 93 protons are what make an atom neptunium. A neutral neptunium atom also has 93 electrons, while isotopes can have different neutron counts without changing the element.
Key point: Atomic number = proton count.
What is neptunium’s electron configuration?
Short answer: [Rn] 5f⁴ 6d¹ 7s² is the standard ground-state reference.
The neutral-atom ground-state reference used on this page is [Rn] 5f⁴ 6d¹ 7s². This is an isolated-atom reference: bonding and ion formation can change which outer electrons are present or chemically active. The listed common oxidation-state context is +3, +4, +5, +6 (important states), which helps connect the atomic configuration to ordinary chemistry without treating electron counting as a single universal rule.
Key point: Electron configuration is a ground-state atomic reference, not a literal picture of every compound.
Is neptunium a metal?
Short answer: Yes. It is a radioactive actinide metal.
This guide classifies Neptunium as an actinide. Its periodic position is Period 7, f-block, Group Actinide. Neptunium follows uranium in the actinide series. Its 5f electrons participate in both complex bonding and multiple oxidation-state chemistry.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
Does neptunium have stable isotopes?
Short answer: No.
²³⁷Np: Radioactive · t½ ≈2.14 million years: Reference teaching nucleus: 93 protons and 144 neutrons. ²³⁹Np: Short-lived radionuclide: Important in the historical discovery chain and nuclear-decay studies.
Key point: Radioactivity is isotope-specific; do not apply one isotope’s nuclear behavior to every atom of the element.
What is neptunium used for?
Short answer: Mostly scientific/nuclear research and measurement contexts rather than ordinary consumer products.
Scientific research: Neptunium supports actinide, nuclear-structure, spectroscopy and materials research. Nuclear measurement: Selected isotopes are relevant to analytical standards, monitoring and nuclear-science studies. Neptunium is primarily a research/nuclear-science element. Element Lookup explains measured atomic, isotope and phase behavior without providing material-production, separation or handling instructions.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Why are three solid structures shown?
Short answer: Neptunium undergoes α→β→γ allotrope transitions as it is heated before melting.
Neptunium has three established solid allotropes across temperature: α (orthorhombic), β (tetragonal) and γ (BCC). Viewers are teaching schematics; exact crystallographic coordinates are not implied. 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 Neptunium
- Royal Society of Chemistry - Neptunium
- NIST - Atomic Data for Neptunium
- IUPAC / evaluated actinide references
Questions to ask next about Neptunium
A good element lesson should lead to the next useful question, not end after a list of facts.
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