Element identity
Atomic number, periodic identity and reference mass/isotope conventions are established and source-reviewed.
Atomic / electronic model
Atomic configurations and orbital teaching models are reference interpretations; heavy-element electronic structure is more complex than a classical shell picture.
Nuclear / isotope data
Half-lives, isotope identities and decay information are taken from evaluated nuclear-data/reference sources and remain isotope-specific.
Material / phase data
Ordinary bulk and phase values are shown only where defensible; solid-state transitions are kept separate from melting.
Geography / safety boundary
Occurrence, discovery and public research context may be mapped. Operational radioactive-material inventories, access routes and sensitive facility details are intentionally not mapped.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Americium (Am)
Americium is element 95, a synthetic radioactive actinide first produced in 1944. Its best-known public application is the tiny sealed ²⁴¹Am source in many ionization smoke alarms, while its chemistry is dominated by actinide oxidation states and isotope-specific nuclear behavior.
Americium atomic number, mass, electron configuration and key properties
Americium: quick answers
How many protons, neutrons and electrons does americium have?
Americium’s atomic number is 95, so every americium atom has 95 protons, and a neutral atom also has 95 electrons. Americium has no stable isotopes, so the number of neutrons depends on which isotope you mean.
What is the symbol for americium?
The chemical symbol for americium is Am.
Is americium a solid, liquid or gas at room temperature?
Americium is a solid at room temperature (about 25 °C).
What family (group) is americium in?
Americium 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 americium?
The ground-state electron configuration of americium is [Rn] 5f⁷ 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.
Ninety-five protons define americium; every isotope shares that proton count.
The half-filled 5f⁷ reference is a useful starting point for actinide chemistry.
Americium follows plutonium in the actinide series.
Americium has no stable isotopes; isotope identity controls half-life and decay.
Radioactivity is a nuclear property distinct from americium oxidation-state chemistry.
Americium in its period and family
Americium is an actinide in Period 7, between plutonium and curium. Its half-filled 5f⁷ ground-state subshell is a useful atomic reference, but actinide chemistry and solid-state behavior are many-electron and strongly context dependent.
Americium Visual Lab
Decode americium’s tile, rotate a ²⁴¹Am teaching nucleus and close-packed metal cell, inspect 7s and representative 5f probability models, then connect the element to discovery history, smoke-alarm context, isotope evidence and regulated research.
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.
Americium in one minute
Atomic number 95 means every americium nucleus contains 95 protons.
The neutral ground-state reference is [Rn] 5f⁷ 7s².
Americium has no stable isotopes; ²⁴¹Am and ²⁴³Am are important long-lived isotopes.
Americium was first made in 1944 at the University of Chicago by Seaborg and colleagues.
Americium applications are regulated radioactive-material contexts; Element Lookup stays educational and non-operational.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 25 · 8 · 2 electrons
The 7s view is spherically symmetric in this nonrelativistic teaching model. The 5f view is explicitly a representative qualitative f-orbital angular form; an f subshell contains seven spatial orbitals, and heavy-actinide relativistic/many-electron effects mean no single cloud is ‘the 5f subshell.’
Room-temperature alpha-americium is double-hexagonal close-packed (DHCP). The viewer is a reviewed teaching cell for the ground-state metallic phase, not a handling model or a complete high-temperature phase diagram.. 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 7s view is spherically symmetric in this nonrelativistic teaching model. The 5f view is explicitly a representative qualitative f-orbital angular form; an f subshell contains seven spatial orbitals, and heavy-actinide relativistic/many-electron effects mean no single cloud is ‘the 5f subshell.’
Where do I meet americium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Smoke alarms
Many ionization smoke alarms use a tiny sealed ²⁴¹Am source. The device is regulated and should be handled/disposed of according to local rules, not dismantled for the source.
How a tiny sealed source can help detect smoke
Americium-241 is best known publicly from ionization smoke alarms; the useful idea is ionization physics, not access to the source.
Sealed Am-241
A tiny sealed radioactive source is part of an engineered detector; it is not a material for user handling.
Plutonium, americium and curium
Across this part of the actinide series, 5f occupancy changes while every isotope remains a separate nuclear system with its own half-life and decay behavior.
| Reference config. | [Rn] 5f⁶ 7s² |
|---|---|
| Context | multiple allotropes |
| Reference config. | [Rn] 5f⁷ 7s² |
|---|---|
| Common chemistry | Am(III) |
| Stable isotopes | none |
| Reference config. | [Rn] 5f⁷ 6d 7s² |
|---|---|
| Context | later actinide |
Americium 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 | 95 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [243] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Rn] 5f⁷ 7s² | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group Actinides · Period 7 · f-block | Periodic-table placement | Evaluated |
| Electronegativity | Not conventionally assigned | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ²⁴¹Am | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Radioactive solid at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | ≈12 g/cm³ · RSC reference | Source-reviewed; see Sources below | Predicted |
| Material / molecular structure | Double-hexagonal close-packed (DHCP) americium metal | Room-temperature alpha-americium is double-hexagonal close-packed (DHCP). The viewer is a reviewed teaching cell for the ground-state metallic phase, not a handling model or a complete high-temperature phase diagram. | Measured |
| Classification | Actinide · radioactive synthetic element | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Room-temperature alpha-americium is double-hexagonal close-packed (DHCP). The viewer is a reviewed teaching cell for the ground-state metallic phase, not a handling model or a complete high-temperature phase diagram. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 1449 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 2284 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | This learner track shows americium as a solid below the 1449 K reference melting point, liquid to about 2284 K and gas above. The room-temperature structure is shown separately; high-temperature solid-phase complexity is not expanded into invented precise boundaries here. | 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 most common; +2/+4/+5/+6 known | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Am³⁺ | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Americium is an actinide in Period 7, between plutonium and curium. Its half-filled 5f⁷ ground-state subshell is a useful atomic reference, but actinide chemistry and solid-state behavior are many-electron and strongly context dependent. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²⁴¹Am | Radioactive · half-life ≈432.7 y | The most familiar americium isotope because of smoke-alarm and source applications; it alpha-decays. | Evaluated |
| ²⁴³Am | Radioactive · half-life ≈7,370 y | A longer-lived isotope important in actinide research and nuclear-data work. | Evaluated |
| Americium isotope family | No stable isotopes | Every americium isotope is radioactive; neutron number changes isotope behavior without changing atomic number 95. | Evaluated |
| Teaching nucleus | ²⁴¹Am · 95 protons + 146 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic and isotope values are measured/evaluated reference data. Published density values differ among reference compilations; this page uses the RSC fact-box value and records that choice in the release research notes. The material viewer is a room-temperature teaching cell, while nuclear applications remain high-level and non-operational. | Evidence summary for this guide | Reviewed |
| Structure evidence | Room-temperature alpha-americium is double-hexagonal close-packed (DHCP). The viewer is a reviewed teaching cell for the ground-state metallic phase, not a handling model or a complete high-temperature phase diagram. | 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 Americium a solid, liquid or gas? State at temperature
This learner track shows americium as a solid below the 1449 K reference melting point, liquid to about 2284 K and gas above. The room-temperature structure is shown separately; high-temperature solid-phase complexity is not expanded into invented precise boundaries here.
Where on Earth is Americium found or produced?
Who discovered Americium, and when?
Glenn Seaborg, Ralph James, Leon Morgan and Albert Ghiorso produced americium at the University of Chicago.
Seaborg revealed the existence of elements 95 and 96 publicly around the time their discovery was being announced.
²⁴¹Am became useful as a compact alpha source in regulated devices and scientific applications.
Americium remains important in smoke-alarm history, actinide chemistry, isotope science and specialized research.
How americium enters research and devices: high-level nuclear context
Americium is a synthetic transuranic element; measurable quantities arise through nuclear transformations of heavier-element fuel/material streams under controlled conditions.
Isotope identity is essential because each americium isotope has its own half-life and nuclear behavior.
Purified americium compounds and sealed sources are produced and managed only in licensed, specialized facilities; Element Lookup does not provide preparation or separation instructions.
Applications use tightly controlled quantities and are governed by radiation-safety, transport and disposal requirements.
What is americium used for?
Ionization smoke alarms
A tiny sealed ²⁴¹Am source ionizes air in a sensing chamber; smoke changes the electrical signal and triggers the alarm.
Scientific research
Americium supports actinide chemistry, spectroscopy, nuclear-data and materials research.
Specialized sources
Americium isotopes can serve as compact radiation sources in controlled scientific/industrial equipment.
Potential space-power studies
Long-lived americium isotopes have been evaluated for specialized radioisotope power concepts.
Americium isotopes and natural abundance
²⁴¹Am
Radioactive · half-life ≈432.7 yThe most familiar americium isotope because of smoke-alarm and source applications; it alpha-decays.
²⁴³Am
Radioactive · half-life ≈7,370 yA longer-lived isotope important in actinide research and nuclear-data work.
Americium isotope family
No stable isotopesEvery americium isotope is radioactive; neutron number changes isotope behavior without changing atomic number 95.
Five-question Americium check
What is americium’s atomic number?
Which isotope is widely associated with ionization smoke alarms?
Does americium have stable isotopes?
What is the neutral ground-state reference configuration?
Which statement is correct?
Americium 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 americium?
Short answer: Americium is synthetic radioactive chemical element 95 in the actinide series.
Atomic number 95 means every americium nucleus contains 95 protons. In the periodic table, Americium is classified here as an actinide · radioactive synthetic element in Period 7 and Group Actinides. Americium is an actinide in Period 7, between plutonium and curium. Its half-filled 5f⁷ ground-state subshell is a useful atomic reference, but actinide chemistry and solid-state behavior are many-electron and strongly context dependent.
Key point: Am is element 95; its periodic position and electron structure explain the rest of the page.
What is americium used for?
Short answer: Its best-known public use is the tiny sealed ²⁴¹Am source in many ionization smoke alarms; it also has specialized scientific uses.
Ionization smoke alarms: A tiny sealed ²⁴¹Am source ionizes air in a sensing chamber; smoke changes the electrical signal and triggers the alarm. Scientific research: Americium supports actinide chemistry, spectroscopy, nuclear-data and materials research. Americium’s chemical identity and its radioactivity must be taught together but not confused. +3 chemistry concerns electrons; half-life and alpha decay depend on the isotope’s nucleus.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Where is americium found?
Short answer: It is not a mined commodity. Tiny natural traces may occur from nuclear processes, but usable americium is produced in controlled nuclear-material contexts.
Americium is a synthetic transuranic element; measurable quantities arise through nuclear transformations of heavier-element fuel/material streams under controlled conditions. The Geography Explorer keeps natural occurrence separate from resources, industrial production and recycling, because those datasets answer different questions about americium.
Key point: Natural occurrence, resources, production and recycling are different geography questions.
What is americium’s electron configuration?
Short answer: The neutral ground-state reference is [Rn] 5f⁷ 7s².
The neutral-atom ground-state reference used on this page is [Rn] 5f⁷ 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 most common; +2/+4/+5/+6 known, 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 americium radioactive?
Short answer: Yes. Americium has no stable isotopes.
²⁴¹Am: Radioactive · half-life ≈432.7 y: The most familiar americium isotope because of smoke-alarm and source applications; it alpha-decays. ²⁴³Am: Radioactive · half-life ≈7,370 y: A longer-lived isotope important in actinide research and nuclear-data work.
Key point: Radioactivity is isotope-specific; do not apply one isotope’s nuclear behavior to every atom of the element.
Is americium safe in a smoke alarm?
Short answer: Commercial alarms use a tiny sealed source engineered and regulated for the device. Users should not dismantle the source and should follow local disposal guidance.
Americium is radioactive. This page stays conceptual and non-operational: it does not provide source dismantling, isotope separation, concentration, fabrication, criticality or other radioactive-material handling instructions.
Key point: Safety claims must be substance- and exposure-specific.
Scientific sources for Americium
- Royal Society of Chemistry - Americium
- NIST - Atomic Data for Americium
- Los Alamos National Laboratory - Americium
- WebElements - Americium crystal structure
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