Element 24 of Periodic table is Chromium with atomic number 24, atomic weight 51.9961. Chromium, symbol Cr, has a Body Centered Cubic structure and Silver color. Chromium is a transition metal element. Know everything about Chromium Facts, Physical Properties, Chemical Properties, Electronic configuration, Atomic and Crystal Structure.
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.
Read key information and facts about element Chromium
| Name | Chromium |
| Atomic Number | 24 |
| Atomic Symbol | Cr |
| Atomic Weight | 51.9961 |
| Phase | Solid |
| Color | Silver |
| Classification | transition metal |
| Group in Periodic Table | 6 |
| Group Name | chromium family |
| Period in Periodic Table | 4 |
| Block in Periodic Table | d-block |
| Electronic Configuration | [Ar] 3d5 4s1 |
| Melting Point | 1907 °C |
| Boiling Point | 2671 °C |
| Electronic Shell Structure | [2, 8, 13, 1] |
| CAS Number | CAS7440-47-3 |
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.
The element Chromium was discovered by Louis Nicolas Vauquelin in year 1797 in France . Chromium derived its name from the Greek word chroma, meaning 'color'
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 %) | |
|---|---|
| Abundance in Universe | 1.5e-05 |
| Abundance in Sun | 2e-05 |
| Abundance in Meteorites | 0.003 |
| Abundance in Earth's Crust | 0.00014 |
| Abundance in Oceans | 6×10-8% |
| Abundance in Humans | 3×10-6% |
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.
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 | 291 | 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 |
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 |
| Oxidation State |
-4;-2;-1
1;2;3;4;5;6 |
| Atomic Term Symbol (Quantum Numbers) | 7S3 |
Shell Structure of Chromium - Electrons per energy level
| n | s | p | d | f | |
|---|---|---|---|---|---|
| 1 | K | 2 | |||
| 2 | L | 2 | 6 | ||
| 3 | M | 2 | 6 | 5 | |
| 4 | N | 1 |
The ground state 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.
Complete ground state electronic configuration for the Chromium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d5 4s1
Chromium atomic radius is 166 pm, while it's covalent radius is 127 pm.
| Atomic Radius |
166 pm (1.66 Å) |
| Atomic Volume | 7.28236694678 cm3 |
| Covalent Radius | 127 pm (1.27 Å) |
| Van der Waals Radius | N/A |
| Neutron Cross Section | 3.1 σa/barns |
The electron affinity of Chromium is 64.3 kJ/mol
| Valence | 6 |
| Electronegativity | 1.66 |
| ElectronAffinity | 64.3 kJ/mol |
Refer to table below for Ionization energies of Chromium
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1 | 652.9 |
| 2 | 1590.6 |
| 3 | 2987 |
| 4 | 4743 |
| 5 | 6702 |
| 6 | 8744.9 |
| 7 | 15455 |
| 8 | 17820 |
| 9 | 20190 |
| 10 | 23580 |
| 11 | 26130 |
| 12 | 28750 |
| 13 | 34230 |
| 14 | 37066 |
| 15 | 97510 |
| 16 | 1.058×105 |
| 17 | 1.143×105 |
| 18 | 1.253×105 |
| 19 | 1.347×105 |
| 20 | 1.443×105 |
| 21 | 1.577×105 |
Refer to below table for Chromium Physical Properties
| Density | 7.14 g/cm3 |
| Molar Volume | 7.28236694678 cm3 |
| Young Modulus | 279 GPa |
| Shear Modulus | 115 GPa |
| Bulk Modulus | 160 GPa |
| Poisson Ratio | 0.21 |
| Mohs Hardness | 8.5 MPa |
| Vickers Hardness | 1060 MPa |
| Brinell Hardness | 1120 MPa |
Chromium is Conductor of electricity. Refer to table below for the Electrical properties of Chromium
| Electrical Conductivity | 7.9×106 S/m |
| Resistivity | 1.3×10-7 m Ω |
| Superconducting Point | N/A |
| Thermal Conductivity | 94 W/(m K) |
| Thermal Expansion | 4.9×10-6 K-1 |
| Magnetic Type | Antiferromagnetic |
| Curie Point | N/A |
| Mass Magnetic Susceptibility | 4.45×10-8 |
| Molar Magnetic Susceptibility | 2.314×10-9 |
| Volume Magnetic Susceptibility | 0.0003177 |
| Refractive Index | N/A |
| Speed of Sound | 5940 m/s |
Refer to table below for Thermal properties of Chromium
| Melting Point | 2180 K (1907 °C) |
| Boiling Point | 2944 K (2671 °C) |
| Critical Temperature | N/A |
| Superconducting Point | N/A |
| Heat of Fusion | 20.5 kJ/mol |
| Heat of Vaporization | 339 kJ/mol |
| Heat of Combustion | N/A |
Isotopes of rhodium. Naturally occurring Chromium has 4 stable isotope - 50Cr, 52Cr, 53Cr, 54Cr.
| Isotope | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|
| 42Cr | ||||
| 43Cr | ||||
| 44Cr | ||||
| 45Cr | ||||
| 46Cr | ||||
| 47Cr | ||||
| 48Cr | ||||
| 49Cr | ||||
| 50Cr | 4.345% | Stable | N/A | |
| 51Cr | ||||
| 52Cr | 83.789% | Stable | N/A | |
| 53Cr | 9.501% | Stable | N/A | |
| 54Cr | 2.365% | Stable | N/A | |
| 55Cr | ||||
| 56Cr | ||||
| 57Cr | ||||
| 58Cr | ||||
| 59Cr | ||||
| 60Cr | ||||
| 61Cr | ||||
| 62Cr | ||||
| 63Cr | ||||
| 64Cr | ||||
| 65Cr | ||||
| 66Cr | ||||
| 67Cr |
| CAS Number | CAS7440-47-3 |
| RTECS Number | RTECSGB4200000 |
| DOT Hazard Class | 4.1 |
| DOT Numbers | 3089 |
| EU Number | N/A |
| NFPA Fire Rating | 1 |
| NFPA Hazards | N/A |
| NFPA Health Rating | 2 |
| NFPA Reactivity Rating | 1 |
| Autoignition Point | 400 °C |
| Flashpoint | N/A |
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 |
| CID Number | CID23976 |
| Gmelin Number | N/A |
| NSC Number | N/A |
| RTECS Number | RTECSGB4200000 |
Metalloid |
Nonmetals |
| Other Nonmetals | |
| Halogens | Noble Gas |
Metals |
|
| Alkali Metals | Alkaline Earth Metals |
| Transition Metals | Post-Transition Metals |
| Lanthanide | Actinide |