Rubidium Element Information, Facts, Properties, Trends, Uses, Comparison with other elements
Rubidium is a chemical element with symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the Alkali Metal group, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, such as very rapid oxidation in air.
It belongs to group 1 of the periodic table having trivial name alkali metals*. You can also download Printable Periodic Table of Elements Flashcards for Rubidium in a PDF format.
Rubidium Facts
Read key information and facts about element Rubidium
| Name | Rubidium |
| Atomic Number | 37 |
| Atomic Symbol | Rb |
| Atomic Weight | 85.4678 |
| Phase | Solid |
| Color | Silver |
| Appearance | grey white |
| Classification | Alkali Metal |
| Natural Occurance | Primordial |
| Group in Periodic Table | 1 |
| Group Name | lithium family |
| Period in Periodic Table | period 5 |
| Block in Periodic Table | s-block |
| Electronic Configuration | [Kr] 5s1 |
| Electronic Shell Structure (Electrons per shell) | 2, 8, 18, 8, 1 |
| Melting Point | 312.46 K |
| Boiling Point | 961 K |
| CAS Number | CAS7440-17-7 |
How to Locate Rubidium on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 37 to find Rubidium on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Rubidium on periodic table look for cross section of group 1 and period 5 in the modern periodic table.
Rubidium History
The element Rubidium was discovered by R. Bunsen and G. R. Kirchhoff in year 1861 in Germany. Rubidium was first isolated by Hevesy in . Rubidium derived its name from the Latin rubidus, meaning 'deep red'.
| Discovered By | R. Bunsen and G. R. Kirchhoff |
| Discovery Date | 1861 in Germany |
| First Isolation | |
| Isolated by | Hevesy |
Bunsen and Kirchhoff discovered it just a few months after caesium, by observing new spectral lines in the minerallepidolite. Bunsen never obtained a pure sample of the metal, which was later obtained by Hevesy.
Rubidium Uses
Rubidium is used in vacuum tubes to remove trace gases. It also is widely used in photocells and specialized glasses. It can be ionized easily, so it is often used as a spacecraft propellant.
Rubidium Presence: Abundance in Nature and Around Us
The table below shows the abundance of Rubidium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
| ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
|---|---|---|
| Abundance in Universe | 10 | 0.1 |
| Abundance in Sun | 30 | 0.4 |
| Abundance in Meteorites | 3300 | 770 |
| Abundance in Earth's Crust | 60000 | 14000 |
| Abundance in Oceans | 120 | 8.7 |
| Abundance in Humans | 4600 | 340 |
Crystal Structure of Rubidium
The solid state structure of Rubidium is Body Centered Cubic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
| a | b | c |
|---|---|---|
| 558.5 pm | 558.5 pm | 558.5 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
| alpha | beta | gamma |
|---|---|---|
| π/2 | π/2 | π/2 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
| Space Group Name | Im_ 3m |
| Space Group Number | 229 |
| Crystal Structure | Body Centered Cubic |
| Number of atoms per unit cell | 2 |
The number of atoms per unit cell in a simple cubic, face-centered cubic and body-centred cubic are 1,4,2 respectively.
Rubidium Atomic and Orbital Properties
Rubidium atoms have 37 electrons and the electronic shell structure is [2, 8, 18, 8, 1] with Atomic Term Symbol (Quantum Numbers) 2S1/2.
| Atomic Number | 37 |
| Number of Electrons (with no charge) | 37 |
| Number of Protons | 37 |
| Mass Number | 85 |
| Number of Neutrons | 48 |
| Shell structure (Electrons per energy level) | 2, 8, 18, 8, 1 |
| Electron Configuration | [Kr] 5s1 |
| Valence Electrons | 5s1 |
| Valence (Valency) | 1 |
| Main Oxidation States | 1 |
| Oxidation States | -1, 1 |
| Atomic Term Symbol (Quantum Numbers) | 2S1/2 |
Bohr Atomic Model of Rubidium - Electrons per energy level
| n | s | p | d | f |
|---|
Ground State Electronic Configuration of Rubidium - neutral Rubidium atom
Abbreviated electronic configuration of Rubidium
The ground state abbreviated electronic configuration of Neutral Rubidium atom is [Kr] 5s1. The portion of Rubidium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Kr]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 5s1, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Rubidium
Complete ground state electronic configuration for the Rubidium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s1
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.
As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.
Atomic Structure of Rubidium
Rubidium atomic radius is 265 pm, while it's covalent radius is 211 pm.
| Atomic Radius Calculated | 265 pm(2.65 Å) |
| Atomic Radius Empirical | 235 pm (2.35 Å) |
| Atomic Volume | 55.788 cm3/mol |
| Covalent Radius | 211 pm (2.11 Å) |
| Van der Waals Radius | 303 pm |
| Neutron Cross Section | 0.38 |
| Neutron Mass Absorption | 0.0003 |
Spectral Lines of Rubidium - Atomic Spectrum of Rubidium
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules.
Spectral lines are the result of interaction between a quantum system and a single photon. A spectral line may be observed either as an emission line or an absorption line.
Spectral lines are highly atom-specific, and can be used to identify the chemical composition of any medium. Several elements, including helium, thallium, and caesium, were discovered by spectroscopic means. They are widely used to determine the physical conditions of stars and other celestial bodies that cannot be analyzed by other means.
Emission spectrum of Rubidium
Absorption spectrum of Rubidium
Rubidium Chemical Properties: Rubidium Ionization Energies and electron affinity
The electron affinity of Rubidium is 46.9 kJ/mol.
| Valence | 1 |
| Electronegativity | 0.82 |
| ElectronAffinity | 46.9 kJ/mol |
Ionization Energy of Rubidium
Ionization energy is the amount of energy required to remove an electron from an atom or molecule.in chemistry, this energy is expresed in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).
Refer to table below for Ionization energies of Rubidium
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1st | 403 |
| 2nd | 2633 |
| 3rd | 3860 |
| 4th | 5080 |
| 5th | 6850 |
| 6th | 8140 |
| 7th | 9570 |
| 8th | 13120 |
| 9th | 14500 |
| 10th | 26740 |
Rubidium Physical Properties
Refer to below table for Rubidium Physical Properties
| Density | 1.532 g/cm3(when liquid at m.p density is $1.46 g/cm3) |
| Molar Volume | 55.788 cm3/mol |
Elastic Properties
| Young Modulus | 2.4 |
| Shear Modulus | - |
| Bulk Modulus | 2.5 GPa |
| Poisson Ratio | - |
Hardness of Rubidium - Tests to Measure of Hardness of Element
| Mohs Hardness | 0.3 MPa |
| Vickers Hardness | - |
| Brinell Hardness | 0.216 MPa |
Rubidium Electrical Properties
Electrical resistivity measures element's electrical resistance or how strongly it resists electric current.The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). While Electrical conductivity is the reciprocal of electrical resistivity. It represents a element's ability to conduct electric current. The SI unit of electrical conductivity is siemens per metre (S/m).
Rubidium is a conductor of electricity. Refer to table below for the Electrical properties of Rubidium
| Electrical conductors | Conductor |
| Electrical Conductivity | 8300000 S/m |
| Resistivity | 1.2e-7 m Ω |
| Superconducting Point | - |
Rubidium Heat and Conduction Properties
| Thermal Conductivity | 58 W/(m K) |
| Thermal Expansion | - |
Rubidium Magnetic Properties
| Magnetic Type | Paramagnetic |
| Curie Point | - |
| Mass Magnetic Susceptibility | 2.6e-9 m3/kg |
| Molar Magnetic Susceptibility | 2.22e-10 m3/mol |
| Volume Magnetic Susceptibility | 0.00000398 |
Optical Properties of Rubidium
| Refractive Index | - |
Acoustic Properties of Rubidium
| Speed of Sound | 1300 m/s |
Rubidium Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Rubidium
| Melting Point | 312.46 K(39.31 °C, 102.758 °F) |
| Boiling Point | 961 K(687.85 °C, 1270.130 °F) |
| Critical Temperature | 2093 K |
| Superconducting Point | - |
Enthalpies of Rubidium
| Heat of Fusion | 2.19 kJ/mol |
| Heat of Vaporization | 72 kJ/mol |
| Heat of Combustion | - |
Rubidium Isotopes - Nuclear Properties of Rubidium
Rubidium has 32 isotopes, with between 71 and 102 nucleons. Rubidium has 1 stable naturally occuring isotopes.
Isotopes of Rubidium - Naturally occurring stable Isotopes: 85Rb.
| Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|---|---|
| 71Rb | 37 | 34 | 71 | Synthetic | ||
| 72Rb | 37 | 35 | 72 | Synthetic | ||
| 73Rb | 37 | 36 | 73 | Synthetic | ||
| 74Rb | 37 | 37 | 74 | Synthetic | ||
| 75Rb | 37 | 38 | 75 | Synthetic | ||
| 76Rb | 37 | 39 | 76 | Synthetic | ||
| 77Rb | 37 | 40 | 77 | Synthetic | ||
| 78Rb | 37 | 41 | 78 | Synthetic | ||
| 79Rb | 37 | 42 | 79 | Synthetic | ||
| 80Rb | 37 | 43 | 80 | Synthetic | ||
| 81Rb | 37 | 44 | 81 | Synthetic | ||
| 82Rb | 37 | 45 | 82 | Synthetic | ||
| 83Rb | 37 | 46 | 83 | Synthetic | ||
| 84Rb | 37 | 47 | 84 | Synthetic | ||
| 85Rb | 37 | 48 | 85 | 72.17% | Stable | |
| 86Rb | 37 | 49 | 86 | Synthetic | ||
| 87Rb | 37 | 50 | 87 | 27.83% | Stable | N/A |
| 88Rb | 37 | 51 | 88 | Synthetic | ||
| 89Rb | 37 | 52 | 89 | Synthetic | ||
| 90Rb | 37 | 53 | 90 | Synthetic | ||
| 91Rb | 37 | 54 | 91 | Synthetic | ||
| 92Rb | 37 | 55 | 92 | Synthetic | ||
| 93Rb | 37 | 56 | 93 | Synthetic | ||
| 94Rb | 37 | 57 | 94 | Synthetic | ||
| 95Rb | 37 | 58 | 95 | Synthetic | ||
| 96Rb | 37 | 59 | 96 | Synthetic | ||
| 97Rb | 37 | 60 | 97 | Synthetic | ||
| 98Rb | 37 | 61 | 98 | Synthetic | ||
| 99Rb | 37 | 62 | 99 | Synthetic | ||
| 100Rb | 37 | 63 | 100 | Synthetic | ||
| 101Rb | 37 | 64 | 101 | Synthetic | ||
| 102Rb | 37 | 65 | 102 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
The United States Department of Transportation (DOT) identifies hazard class of all dangerous elements/goods/commodities either by its class (or division) number or name. The DOT has divided these materials into nine different categories, known as Hazard Classes.
| DOT Numbers | 1423 |
| DOT Hazard Class | 4.3 |
NFPA 704 is a Standard System for the Identification of the Hazards of Materials for Emergency Response. NFPA is a standard maintained by the US based National Fire Protection Association.
The health (blue), flammability (red), and reactivity (yellow) rating all use a numbering scale ranging from 0 to 4. A value of zero means that the element poses no hazard; a rating of four indicates extreme danger.
| NFPA Fire Rating | 3 | Flash Points below 37.8°C (100°F) |
| NFPA Health Rating | 2 | Flash Points Above 37.8°C (100°F) not exceeding 93.3°C (200°F) |
| NFPA Reactivity Rating | ||
| NFPA Hazards | Water Reactive |
| Autoignition Point | - |
| Flashpoint | - |
Database Search
List of unique identifiers to search the element in various chemical registry databases
| Database | Identifier number |
|---|---|
| CAS Number - Chemical Abstracts Service (CAS) | CAS7440-17-7 |
| RTECS Number | RTECSVL8500000 |
| CID Number | CID5357696 |
| Gmelin Number | - |
| NSC Number | - |
Compare Rubidium with other elements
Compare Rubidium with Group 1, Period 5 and Alkali Metal elements of the periodic table.
Compare Rubidium with all Group 1 elements
Compare Rubidium with all Period 5 elements
Compare Rubidium with all Alkali Metal elements
Frequently Asked Questions (FAQ)
Find the answers to the most frequently asked questions about Rubidium