Atomic / phase data
Reference values are evaluated.
BCC structure
Ordinary rubidium metal is represented as BCC.
⁸⁷Rb geochronology
The ⁸⁷Rb→⁸⁷Sr decay system is experimentally established.
Occurrence geography
Mineral occurrence is conceptual rather than fake native-metal pins.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Rubidium (Rb)
Rubidium is element 37, a soft Group 1 metal with one 5s valence electron. Beyond its high reactivity, rubidium connects atomic spectroscopy, Rb–Sr geochronology and laser-cooled atomic physics.
Rubidium atomic number, mass, electron configuration and key properties
Rubidium: quick answers
How many protons, neutrons and electrons does rubidium have?
Rubidium’s atomic number is 37, so every rubidium atom has 37 protons, and a neutral atom also has 37 electrons. Its most common natural isotope, rubidium-85, has 48 neutrons (other isotopes have different neutron counts).
What is the symbol for rubidium?
The chemical symbol for rubidium is Rb.
Is rubidium a solid, liquid or gas at room temperature?
Rubidium is a solid at room temperature (about 25 °C).
What family (group) is rubidium in?
Rubidium is an alkali metal, in group 1, period 5 of the periodic table.
How many valence electrons does rubidium have?
Rubidium has 1 valence electron, the single electron in its outer shell, which matches its position in group 1.
What is the electron configuration of rubidium?
The ground-state electron configuration of rubidium is [Kr] 5s¹.
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.
37 protons define rubidium.
The reference ground-state configuration frames atomic and chemical behavior.
Periodic position organizes recurring trends without replacing element-specific evidence.
The teaching nucleus is one isotope, not the relative atomic mass.
Phase claims preserve measured/evaluated/predicted/unknown evidence labels.
Rubidium in its period and family
Rubidium is the Period 5 alkali metal below potassium and above cesium. The single 5s electron supports strong +1 chemistry and very low ionization energy relative to many elements.
Rubidium Visual Lab
Toggle Rb to Rb⁺, rotate a ⁸⁵Rb teaching nucleus and BCC cell, inspect the spherical 5s probability cloud, then connect the atom to spectroscopy and the ⁸⁷Rb→⁸⁷Sr geological clock.
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.
Rubidium in one minute
Atomic number 37 means 37 protons.
Neutral rubidium ends in 5s¹ and commonly forms Rb⁺.
Rubidium metal is BCC near room temperature.
⁸⁷Rb is naturally radioactive and is used in Rb–Sr geochronology.
Rubidium also has important roles in atomic-physics and frequency-standard research.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 8 · 1 electrons
The 5s cloud is an isolated-atom probability model. It is not an electron orbit and does not depict conduction electrons in metallic rubidium.
Rubidium metal is represented with a body-centred-cubic conventional teaching cell near room temperature. Boundary atoms are shared between neighbouring cells.. 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 5s cloud is an isolated-atom probability model. It is not an electron orbit and does not depict conduction electrons in metallic rubidium.
Where do I meet rubidium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Spectroscopy
Rubidium has strong optical transitions used in laser spectroscopy and atomic-physics experiments.
Rb atom → Rb⁺ ion → ⁸⁷Rb geological clock
One outer 5s electron connects alkali-metal chemistry to atomic spectroscopy, while isotope identity adds a separate geological clock.
[Kr] 5s¹
Neutral rubidium has one outer 5s electron.
Potassium, rubidium and cesium
One outer s electron repeats down the alkali metals while size and phase properties change.
| Outer | 4s¹ |
|---|---|
| Melt | 336.5 K |
| Outer | 5s¹ |
|---|---|
| Melt | 312.45 K |
| Outer | 6s¹ |
|---|---|
| Melt | 301.7 K |
Rubidium 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 | 37 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | 85.468 | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Kr] 5s¹ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 1 · Period 5 · s-block | Periodic-table placement | Evaluated |
| Electronegativity | 0.82 | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ⁸⁵Rb | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Soft silvery alkali metal · solid at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | 1.53 g/cm³ | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Rubidium metal · body-centred cubic | Rubidium metal is represented with a body-centred-cubic conventional teaching cell near room temperature. Boundary atoms are shared between neighbouring cells. | Measured |
| Classification | Alkali metal | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Rubidium metal is represented with a body-centred-cubic conventional teaching cell near room temperature. Boundary atoms are shared between neighbouring cells. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 312.45 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 961 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | At approximately standard pressure, rubidium is BCC solid below 312.45 K, liquid to about 961 K, and gaseous above that boiling reference. | 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 |
|---|---|---|---|
| Ordinary electrical behavior | Metallic conductor | Qualitative bulk behavior; exact resistivity depends on temperature, purity and alloy state. | Measured |
| Conduction model | Collective solid-state electrons | Do not interpret isolated-atom orbital clouds as literal current paths. | Reviewed |
| Surface / compound caveat | Oxides, salts and alloys can behave differently from the pure metal | Material context | Reviewed |
| Engineering values | Condition-dependent | Use condition-specific materials data for engineering calculations. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | +1 | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Rb⁺ | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Rubidium is the Period 5 alkali metal below potassium and above cesium. The single 5s electron supports strong +1 chemistry and very low ionization energy relative to many elements. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ⁸⁵Rb | Stable natural isotope | Reference teaching nucleus with 37 protons and 48 neutrons. | Evaluated |
| ⁸⁷Rb | Very long-lived radioactive natural isotope | Decays to ⁸⁷Sr and underpins Rb–Sr geochronology. | Evaluated |
| Rubidium isotope context | Two major natural isotopes | Natural rubidium includes both ⁸⁵Rb and ⁸⁷Rb. | Evaluated |
| Teaching nucleus | ⁸⁵Rb · 37 protons + 48 neutrons | Reference isotope used in the nucleus model | Reviewed |
Is Rubidium a solid, liquid or gas? State at temperature
At approximately standard pressure, rubidium is BCC solid below 312.45 K, liquid to about 961 K, and gaseous above that boiling reference.
Where on Earth is Rubidium found or produced?
Who discovered Rubidium, and when?
Robert Bunsen and Gustav Kirchhoff discovered rubidium by spectroscopy, identifying characteristic red spectral lines.
Rubidium spectroscopy and isotope science became important research tools.
The ⁸⁷Rb→⁸⁷Sr decay system became a major method for dating geological materials.
Rubidium is used mainly in specialized research, timing and electronic/atomic applications rather than bulk structural materials.
From mineral association to specialized rubidium products
Rubidium occurs as a minor constituent in minerals and brines associated with alkali metals.
Industrial recovery separates rubidium compounds from larger alkali-metal process streams.
High-purity compounds or metal are produced for specialized technical uses; this guide does not provide reactive-metal preparation procedures.
Atomic-physics applications use controlled laboratory systems, not bulk consumer rubidium.
What is rubidium used for?
Atomic clocks
Rubidium frequency standards provide compact, stable timing references.
Research
Laser cooling, spectroscopy and quantum/atomic experiments use rubidium atoms.
Geochronology
⁸⁷Rb/⁸⁷Sr measurements constrain ages and geological histories.
Specialty electronics
Rubidium compounds have niche photoelectric and electronic uses.
Rubidium isotopes and natural abundance
⁸⁵Rb
Stable natural isotopeReference teaching nucleus with 37 protons and 48 neutrons.
⁸⁷Rb
Very long-lived radioactive natural isotopeDecays to ⁸⁷Sr and underpins Rb–Sr geochronology.
Rubidium isotope context
Two major natural isotopesNatural rubidium includes both ⁸⁵Rb and ⁸⁷Rb.
Five-question Rubidium check
What is rubidium’s atomic number?
What is the common ion?
What is the outer configuration?
Which isotope system is used in geochronology?
What structure is shown for room-temperature rubidium?
Rubidium 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 rubidium?
Short answer: Rubidium is element 37, a soft reactive alkali metal.
Atomic number 37 means every rubidium nucleus contains 37 protons. In the periodic table, Rubidium is classified here as an alkali metal in Period 5 and Group 1. Rubidium is the Period 5 alkali metal below potassium and above cesium. The single 5s electron supports strong +1 chemistry and very low ionization energy relative to many elements.
Key point: Rb is element 37; its periodic position and electron structure explain the rest of the page.
How many valence electrons does rubidium have?
Short answer: One, in the 5s¹ outer configuration.
The neutral-atom ground-state reference used on this page is [Kr] 5s¹. 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 +1, 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 rubidium a metal?
Short answer: Yes. It is a Group 1 alkali metal.
This guide classifies Rubidium as an alkali metal. Its periodic position is Period 5, s-block, Group 1. Rubidium is the Period 5 alkali metal below potassium and above cesium. The single 5s electron supports strong +1 chemistry and very low ionization energy relative to many elements.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
What is rubidium used for?
Short answer: Specialized uses include frequency standards, atomic-physics research and Rb–Sr geochronology.
Atomic clocks: Rubidium frequency standards provide compact, stable timing references. Research: Laser cooling, spectroscopy and quantum/atomic experiments use rubidium atoms. Rubidium metal, Rb⁺ salts and radioactive ⁸⁷Rb are related by element identity but are not the same chemical or nuclear object. The page keeps ion chemistry and isotope clocks separate.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Who discovered rubidium?
Short answer: Robert Bunsen and Gustav Kirchhoff in 1861 using spectroscopy.
In 1861, Robert Bunsen and Gustav Kirchhoff discovered rubidium by spectroscopy, identifying characteristic red spectral lines. In the 20th century, Rubidium spectroscopy and isotope science became important research tools.
Key point: Discovery credit follows the historical evidence and accepted attribution, not just the earliest claim.
Where is rubidium found?
Short answer: Dispersed in certain potassium- and lithium-bearing minerals and brines rather than as native metal.
Rubidium occurs as a minor constituent in minerals and brines associated with alkali metals. Mineral occurrence Rubidium occurs dispersed in potassium-rich and lithium-rich minerals rather than as native metal deposits.
Key point: Natural occurrence, resources, production and recycling are different geography questions.
Scientific sources for Rubidium
Questions to ask next about Rubidium
A good element lesson should lead to the next useful question, not end after a list of facts.
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