Chromium Element Information, Facts, Properties, Trends, Uses, Comparison with other elements
Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point.
It belongs to group 6 of the periodic table having trivial name null. You can also download Printable Periodic Table of Elements Flashcards for Chromium in a PDF format.
Chromium Facts
Read key information and facts about element Chromium
| Name | Chromium |
| Atomic Number | 24 |
| Atomic Symbol | Cr |
| Atomic Weight | 51.9961 |
| Phase | Solid |
| Color | Silver |
| Appearance | silvery metallic |
| Classification | Transition Metal |
| Natural Occurance | Primordial |
| Group in Periodic Table | 6 |
| Group Name | chromium family |
| Period in Periodic Table | period 4 |
| Block in Periodic Table | d-block |
| Electronic Configuration | [Ar] 3d5 4s1 |
| Electronic Shell Structure (Electrons per shell) | 2, 8, 13, 1 |
| Melting Point | 2180 K |
| Boiling Point | 2944 K |
| CAS Number | CAS7440-47-3 |
How to Locate Chromium 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 24 to find Chromium 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 Chromium on periodic table look for cross section of group 6 and period 4 in the modern periodic table.
Chromium History
The element Chromium was discovered by N. Vauquelin in year 1797 in France. Chromium was first isolated by N. Vauquelin in 1798. Chromium derived its name from the Greek word chroma, meaning 'color'.
| Discovered By | N. Vauquelin |
| Discovery Date | 1797 in France |
| First Isolation | 1798 |
| Isolated by | N. Vauquelin |
Vauquelin discovered the trioxide incrocoiteore, and later isolated the metal by heating the oxide in a charcoal oven.
Chromium Uses
Chromium is used in stainless steel as well as in the chrome plating process. Various chromium compounds are known for their strong colors.
Chromium Presence: Abundance in Nature and Around Us
The table below shows the abundance of Chromium 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 | 15000 | 400 |
| Abundance in Sun | 20000 | 400 |
| Abundance in Meteorites | 3100000 | 1200000 |
| Abundance in Earth's Crust | 140000 | 55000 |
| Abundance in Oceans | 0.6 | 0.071 |
| Abundance in Humans | 30 | 4 |
Crystal Structure of Chromium
The solid state structure of Chromium 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 |
|---|---|---|
| 291 pm | 291 pm | 291 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.
Chromium Atomic and Orbital Properties
Chromium atoms have 24 electrons and the electronic shell structure is [2, 8, 13, 1] with Atomic Term Symbol (Quantum Numbers) 7S3.
| Atomic Number | 24 |
| Number of Electrons (with no charge) | 24 |
| Number of Protons | 24 |
| Mass Number | 52 |
| Number of Neutrons | 28 |
| Shell structure (Electrons per energy level) | 2, 8, 13, 1 |
| Electron Configuration | [Ar] 3d5 4s1 |
| Valence Electrons | 3d5 4s1 |
| Valence (Valency) | 6 |
| Main Oxidation States | 2, 3, 6 |
| Oxidation States | -4, -2, -1, 0, 1, 2, 3, 4, 5, 6 |
| Atomic Term Symbol (Quantum Numbers) | 7S3 |
Bohr Atomic Model of Chromium - Electrons per energy level
| n | s | p | d | f |
|---|
Ground State Electronic Configuration of Chromium - neutral Chromium atom
Abbreviated electronic configuration of Chromium
The ground state abbreviated electronic configuration of Neutral Chromium atom is [Ar] 3d5 4s1. The portion of Chromium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Ar]. 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 3d5 4s1, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Chromium
Complete ground state electronic configuration for the Chromium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d5 4s1
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 Chromium
Chromium atomic radius is 166 pm, while it's covalent radius is 127 pm.
| Atomic Radius Calculated | 166 pm(1.66 Å) |
| Atomic Radius Empirical | 140 pm (1.4 Å) |
| Atomic Volume | 7.2824 cm3/mol |
| Covalent Radius | 127 pm (1.27 Å) |
| Van der Waals Radius | - |
| Neutron Cross Section | 3.1 |
| Neutron Mass Absorption | 0.0021 |
Spectral Lines of Chromium - Atomic Spectrum of Chromium
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 Chromium
Absorption spectrum of Chromium
Chromium Chemical Properties: Chromium Ionization Energies and electron affinity
The electron affinity of Chromium is 64.3 kJ/mol.
| Valence | 6 |
| Electronegativity | 1.66 |
| ElectronAffinity | 64.3 kJ/mol |
Ionization Energy of Chromium
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 Chromium
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1st | 652.9 |
| 2nd | 1590.6 |
| 3rd | 2987 |
| 4th | 4743 |
| 5th | 6702 |
| 6th | 8744.9 |
| 7th | 15455 |
| 8th | 17820 |
| 9th | 20190 |
| 10th | 23580 |
| 11th | 26130 |
| 12th | 28750 |
| 13th | 34230 |
| 14th | 37066 |
| 15th | 97510 |
| 16th | 105800 |
| 17th | 114300 |
| 18th | 125300 |
| 19th | 134700 |
| 20th | 144300 |
| 21st | 157700 |
| 22nd | 166090 |
| 23rd | 721870 |
| 24th | 761733 |
Chromium Physical Properties
Refer to below table for Chromium Physical Properties
| Density | 7.14 g/cm3(when liquid at m.p density is $6.3 g/cm3) |
| Molar Volume | 7.2824 cm3/mol |
Elastic Properties
| Young Modulus | 279 |
| Shear Modulus | 115 GPa |
| Bulk Modulus | 160 GPa |
| Poisson Ratio | 0.21 |
Hardness of Chromium - Tests to Measure of Hardness of Element
| Mohs Hardness | 8.5 MPa |
| Vickers Hardness | 1060 MPa |
| Brinell Hardness | 1120 MPa |
Chromium 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).
Chromium is a conductor of electricity. Refer to table below for the Electrical properties of Chromium
| Electrical conductors | Conductor |
| Electrical Conductivity | 7900000 S/m |
| Resistivity | 1.3e-7 m Ω |
| Superconducting Point | - |
Chromium Heat and Conduction Properties
| Thermal Conductivity | 94 W/(m K) |
| Thermal Expansion | 0.0000049 /K |
Chromium Magnetic Properties
| Magnetic Type | Antiferromagnetic |
| Curie Point | - |
| Mass Magnetic Susceptibility | 4.45e-8 m3/kg |
| Molar Magnetic Susceptibility | 2.314e-9 m3/mol |
| Volume Magnetic Susceptibility | 0.0003177 |
Optical Properties of Chromium
| Refractive Index | - |
Acoustic Properties of Chromium
| Speed of Sound | 5940 m/s |
Chromium Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Chromium
| Melting Point | 2180 K(1906.85 °C, 3464.330 °F) |
| Boiling Point | 2944 K(2670.85 °C, 4839.530 °F) |
| Critical Temperature | - |
| Superconducting Point | - |
Enthalpies of Chromium
| Heat of Fusion | 20.5 kJ/mol |
| Heat of Vaporization | 339 kJ/mol |
| Heat of Combustion | - |
Chromium Isotopes - Nuclear Properties of Chromium
Chromium has 26 isotopes, with between 42 and 67 nucleons. Chromium has 4 stable naturally occuring isotopes.
Isotopes of Chromium - Naturally occurring stable Isotopes: 50Cr, 52Cr, 53Cr, 54Cr.
| Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|---|---|
| 42Cr | 24 | 18 | 42 | Synthetic | ||
| 43Cr | 24 | 19 | 43 | Synthetic | ||
| 44Cr | 24 | 20 | 44 | Synthetic | ||
| 45Cr | 24 | 21 | 45 | Synthetic | ||
| 46Cr | 24 | 22 | 46 | Synthetic | ||
| 47Cr | 24 | 23 | 47 | Synthetic | ||
| 48Cr | 24 | 24 | 48 | Synthetic | ||
| 49Cr | 24 | 25 | 49 | Synthetic | ||
| 50Cr | 24 | 26 | 50 | 4.345% | Stable | N/A |
| 51Cr | 24 | 27 | 51 | Synthetic | ||
| 52Cr | 24 | 28 | 52 | 83.789% | Stable | |
| 53Cr | 24 | 29 | 53 | 9.501% | Stable | N/A |
| 54Cr | 24 | 30 | 54 | 2.365% | Stable | N/A |
| 55Cr | 24 | 31 | 55 | Synthetic | ||
| 56Cr | 24 | 32 | 56 | Synthetic | ||
| 57Cr | 24 | 33 | 57 | Synthetic | ||
| 58Cr | 24 | 34 | 58 | Synthetic | ||
| 59Cr | 24 | 35 | 59 | Synthetic | ||
| 60Cr | 24 | 36 | 60 | Synthetic | ||
| 61Cr | 24 | 37 | 61 | Synthetic | ||
| 62Cr | 24 | 38 | 62 | Synthetic | ||
| 63Cr | 24 | 39 | 63 | Synthetic | ||
| 64Cr | 24 | 40 | 64 | Synthetic | ||
| 65Cr | 24 | 41 | 65 | Synthetic | ||
| 66Cr | 24 | 42 | 66 | Synthetic | ||
| 67Cr | 24 | 43 | 67 | 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 | 3089 |
| DOT Hazard Class | 4.1 |
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 | 1 | Flash Points Above 93.3°C (200°F) |
| NFPA Health Rating | 2 | Flash Points Above 37.8°C (100°F) not exceeding 93.3°C (200°F) |
| NFPA Reactivity Rating | 1 | Flash Points Above 93.3°C (200°F) |
| NFPA Hazards |
| Autoignition Point | 400 °C |
| 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) | CAS7440-47-3 |
| RTECS Number | RTECSGB4200000 |
| CID Number | CID23976 |
| Gmelin Number | - |
| NSC Number | - |
Compare Chromium with other elements
Compare Chromium with Group 6, Period 4 and Transition Metal elements of the periodic table.
Compare Chromium with all Group 6 elements
Compare Chromium with all Period 4 elements
Compare Chromium with all Transition Metal elements
Frequently Asked Questions (FAQ)
Find the answers to the most frequently asked questions about Chromium