Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (
Help us improve Python packaging - Donate today!

Python API with a database of atomic properties for elements in the periodic table

Project Description

This package provides a convenient python API for accessing various properties of elements, ions and isotopes in the periodic table of elements.

Moreover it provides an easy to use interface to pandas and convenient visualization functionality through bokeh that enables you to create customized periodic tables displaying various properties.

The mendeleev package also supplies convenient tools for dealing with electronic configurations, calculating functions of atomic properties, exploring the periodic trends in the periodic tables. If you want to look at some examples there are a few tutorials available as jupyter notebooks.

Interactive web app

If you would like to explore the data available in mendeleev check out the interactive web app at where you can create your own periodic tables and visualize the relations between various properties of elements.


Following electronegativity scales are available either as stored values or computed on request from other properties:

  • Allen
  • Allred & Rochow
  • Cottrell & Sutton
  • Ghosh
  • Gordy
  • Li & Xue
  • Nagle
  • Martynov & Batsanov
  • Mulliken
  • Pauling
  • Sanderson

The following data are currently available:

Name Type Comment Unit Data Source
abundance_crust float Abundance in the Earth’s crust mg/kg [8]
abundance_sea float Abundance in the seas mg/L [8]
annotation str Annotations regarding the data    
atomic_number int Atomic number    
atomic_radius float Atomic radius pm  
atomic_radius_rahm float Atomic radius by Rahm et al. pm [42]
atomic_volume float Atomic volume cm3/mol  
atomic_weight float Atomic weight   [36], [37]
atomic_weight_uncertainty float Atomic weight uncertainty   [36], [37]
block int Block in periodic table    
boiling_point float Boiling temperature K  
c6 float C_6 dispersion coefficient in a.u. a.u. [1], [2]
c6_gb float C_6 dispersion coefficient in a.u. (Gould & Bučko) a.u. [35]
cas str Chemical Abstracts Serice identifier    
covalent_radius_bragg float Covalent radius by Bragg pm [3]
covalent_radius_cordero float Covalent radius by Cerdero et al. pm [4]
covalent_radius_pyykko float Single bond covalent radius by Pyykko et al. pm [5]
covalent_radius_pyykko_double float Double bond covalent radius by Pyykko et al. pm [46]
covalent_radius_pyykko_triple float Triple bond covalent radius by Pyykko et al. pm [47]
covalent_radius_slater float Covalent radius by Slater pm [6]
cpk_color str Element color in CPK convention HEX [24]
density float Density at 295K g/cm3  
description str Short description of the element    
dipole_polarizability float Dipole polarizability a.u. [7]
discoverers str The discoverers of the element    
discovery_location str The location where the element was discovered    
dipole_year int The year the element was discovered    
electron_affinity float Electron affinity eV [8], [9]
electrons int Number of electrons    
en_allen float Allen’s scale of electronegativity eV [10], [11]
en_ghosh float Ghosh’s scale of electronegativity   [32]
en_mulliken float Mulliken’s scale of electronegativity eV [12]
en_pauling float Pauling’s scale of electronegativity   [8]
econf str Ground state electron configuration    
evaporation_heat float Evaporation heat kJ/mol  
fusion_heat float Fusion heat kJ/mol  
gas_basicity float Gas basicity kJ/mol [8]
geochemical_class str Geochemical classification   [43]
goldschmidt_class str Goldschmidt classification   [43], [44]
group int Group in periodic table    
heat_of_formation float Heat of formation kJ/mol [8]
ionenergy tuple Ionization energies eV [13]
ionic_radii list Ionic and crystal radii in pm pm [14]
is_monoisotopic bool Is the element monoisotopic    
is_radioactive bool Is the element radioactive    
isotopes list Isotopes    
jmol_color str Element color in Jmol convention HEX [25]
lattice_constant float Lattice constant Angstrom  
lattice_structure str Lattice structure code    
mass_number int Mass number (most abundant isotope)    
melting_point float Melting temperature K  
metallic_radius float Single-bond metallic radius pm [45]
metallic_radius_c12 float Metallic radius with 12 nearest neighbors pm [45]
molcas_gv_color str Element color in MOCAS GV convention HEX [26]
name str Name in English    
name_origin str Origin of the name    
neutrons int Number of neutrons (most abundant isotope)    
oxistates list Oxidation states    
period int Period in periodic table    
proton_affinity float Proton affinity kJ/mol [8]
protons int Number of protons    
sconst float Nuclear charge screening constants   [15], [16]
series int Index to chemical series    
sources str Sources of the element    
specific_heat float Specific heat @ 20 C J/(g mol)  
symbol str Chemical symbol    
thermal_conductivity float Thermal conductivity @25 C W/(m K)  
uses str Applications of the element    
vdw_radius float Van der Waals radius pm [8]
vdw_radius_alvarez float Van der Waals radius according to Alvarez pm [33], [34]
vdw_radius_batsanov float Van der Waals radius according to Batsanov pm [17]
vdw_radius_bondi float Van der Waals radius according to Bondi pm [18]
vdw_radius_dreiding float Van der Waals radius from the DREIDING FF pm [19]
vdw_radius_mm3 float Van der Waals radius from the MM3 FF pm [20]
vdw_radius_rt float Van der Waals radius according to Rowland and Taylor pm [21]
vdw_radius_truhlar float Van der Waals radius according to Truhlar pm [22]
vdw_radius_uff float Van der Waals radius from the UFF pm [23]


Name Type Comment Unit Data Source
abundance float Relative Abundance   [38]
g_factor float Nuclear g-factor   [40]
half_life float Half life of the isotope   [36]
half_life_unit str Unit in which the half life is given   [36]
is_radioactive bool Is the isotope radioactive   [39]
mass float Atomic mass Da [39]
mass_number int Mass number of the isotope   [39]
mass_uncertainty float Uncertainty of the atomic mass   [39]
spin float Nuclear spin quantum number    
quadrupole_moment float Nuclear electric quadrupole moment b [100 fm^2] [41]
[1]Chu, X., & Dalgarno, A. (2004). Linear response time-dependent density functional theory for van der Waals coefficients. The Journal of Chemical Physics, 121(9), 4083. doi:10.1063/1.1779576
[2]Tang, K. T., Norbeck, J. M., & Certain, P. R. (1976). Upper and lower bounds of two- and three-body dipole, quadrupole, and octupole van der Waals coefficients for hydrogen, noble gas, and alkali atom interactions. The Journal of Chemical Physics, 64(7), 3063. doi:10.1063/1.432569
[3]Bragg, W. L. (1920). The arrangement of atoms in crystals. Philosophical Magazine, 40(236), 169-189. doi:10.1080/14786440808636111
[4]Cordero, B., Gomez, V., Platero-Prats, A. E., Reves, M., Echeverria, J., Cremades, E., … Alvarez, S. (2008). Covalent radii revisited. Dalton Transactions, (21), 2832. doi:10.1039/b801115j
[5]Pyykko, P., & Atsumi, M. (2009). Molecular Single-Bond Covalent Radii for Elements 1-118. Chemistry - A European Journal, 15(1), 186-197. doi:10.1002/chem.200800987
[6]Slater, J. C. (1964). Atomic Radii in Crystals. The Journal of Chemical Physics, 41(10), 3199. doi:10.1063/1.1725697
[7]P. Schwerdtfeger “Table of experimental and calculated static dipole polarizabilities for the electronic ground states of the neutral elements (in atomic units)”, February 11, 2014 source
[8](1, 2, 3, 4, 5, 6, 7, 8) W. M. Haynes, Handbook of Chemistry and Physics 95th Edition, CRC Press, New York, 2014, ISBN-10: 1482208679, ISBN-13: 978-1482208672.
[9]Andersen, T. (2004). Atomic negative ions: structure, dynamics and collisions. Physics Reports, 394(4-5), 157-313. doi:10.1016/j.physrep.2004.01.001
[10]Mann, J. B., Meek, T. L., & Allen, L. C. (2000). Configuration Energies of the Main Group Elements. Journal of the American Chemical Society, 122(12), 2780-2783. doi:10.1021/ja992866e
[11]Mann, J. B., Meek, T. L., Knight, E. T., Capitani, J. F., & Allen, L. C. (2000). Configuration Energies of the d-Block Elements. Journal of the American Chemical Society, 122(21), 5132-5137. doi:10.1021/ja9928677
[12]Mulliken, R. S. (1934). A New Electroaffinity Scale; Together with Data on Valence States and on Valence Ionization Potentials and Electron Affinities. The Journal of Chemical Physics, 2(11), 782. doi:10.1063/1.1749394
[13]NIST Atomic Database accessed on April 13, 2015
[14]Shannon, R. D. (1976). Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica Section A. doi:10.1107/S0567739476001551
[15]Clementi, E., & Raimondi, D. L. (1963). Atomic Screening Constants from SCF Functions. The Journal of Chemical Physics, 38(11), 2686. doi:10.1063/1.1733573
[16]Clementi, E. (1967). Atomic Screening Constants from SCF Functions. II. Atoms with 37 to 86 Electrons. The Journal of Chemical Physics, 47(4), 1300. doi:10.1063/1.1712084
[17]Batsanov, S. S. (2001). Van der Waals radii of elements. Inorganic Materials, 37(9), 871-885. doi:10.1023/A:1011625728803
[18]Bondi, A. (1964). van der Waals Volumes and Radii. The Journal of Physical Chemistry, 68(3), 441-451. doi:10.1021/j100785a001
[19]Mayo, S. L., Olafson, B. D., & Goddard, W. A. (1990). DREIDING: a generic force field for molecular simulations. The Journal of Physical Chemistry, 94(26), 8897-8909. doi:10.1021/j100389a010
[20]Allinger, N. L., Zhou, X., & Bergsma, J. (1994). Molecular mechanics parameters. Journal of Molecular Structure: THEOCHEM, 312(1), 69-83. doi:10.1016/S0166-1280(09)80008-0
[21]Rowland, R. S., & Taylor, R. (1996). Intermolecular Nonbonded Contact Distances in Organic Crystal Structures: Comparison with Distances Expected from van der Waals Radii. The Journal of Physical Chemistry, 100(18), 7384-7391. doi:10.1021/jp953141+
[22]Mantina, M., Chamberlin, A. C., Valero, R., Cramer, C. J., & Truhlar, D. G. (2009). Consistent van der Waals Radii for the Whole Main Group. The Journal of Physical Chemistry A, 113(19), 5806-5812. doi:10.1021/jp8111556
[23]Rappe, A. K., Casewit, C. J., Colwell, K. S., Goddard, W. A., & Skiff, W. M. (1992). UFF, a full periodic table force field for molecular mechanics and molecular dynamics simulations. Journal of the American Chemical Society, 114(25), 10024-10035. doi:10.1021/ja00051a040
[24]CPK colors
[25]Jmol colors
[26]MOLCAS GV colors
[27]R. T. Sanderson, Chemical Bonds and Bond Energy, Academic Press, New York, 1976, ISBN: 0-12-618060-1
[28]Allen, L. C., & Huheey, J. E. (1980). The definition of electronegativity and the chemistry of the noble gases. Journal of Inorganic and Nuclear Chemistry, 42(10), 1523-1524. doi:10.1016/0022-1902(80)80132-1
[29]Luo, Z., Chen, X., Li, J., & Ning, C. (2016). Precision measurement of the electron affinity of niobium. Physical Review A, 93(2), 020501. doi:10.1103/PhysRevA.93.020501
[30]Chen, X., & Ning, C. (2016). Accurate electron affinity of Co and fine-structure splittings of Co$^-$ via slow-electron velocity-map imaging. Physical Review A, 93(5), 052508. doi:10.1103/PhysRevA.93.052508
[31]Chen, X., & Ning, C. (2016). Accurate electron affinity of Pb and isotope shifts of binding energies of Pb−. The Journal of Chemical Physics, 145(8), 84303. doi:10.1063/1.4961654
[32]Ghosh, D. C. (2005). A New Scale of Electronegativity Based on Absolute Radii of Atoms. Journal of Theoretical and Computational Chemistry, 4(1), 21–33. doi:10.1142/S0219633605001556
[33]Alvarez, S. (2013). A cartography of the van der Waals territories. Dalton Transactions, 42(24), 8617. doi:10.1039/c3dt50599e
[34]Vogt, J., & Alvarez, S. (2014). van der Waals Radii of Noble Gases. Inorganic Chemistry, 53(17), 9260–9266. doi:10.1021/ic501364h
[35]Gould, T., & Bučko, T. (2016). C6 Coefficients and Dipole Polarizabilities for All Atoms and Many Ions in Rows 1-6 of the Periodic Table. Journal of Chemical Theory and Computation, 12(8), 3603–3613. doi:10.1021/acs.jctc.6b00361
[36](1, 2, 3, 4) Meija, J., Coplen, T. B., Berglund, M., Brand, W. A., De Bièvre, P., Gröning, M., Holden, N., Irrgeher, J., Loss, R., Walczyk, T., Prohaska, T. (2016). Atomic weights of the elements 2013 (IUPAC Technical Report). Pure and Applied Chemistry, 88(3), 265–291. doi:10.1515/pac-2015-0305
[37](1, 2) Standard Atomic Weights, IUPAC-CIAAW, accessed Jan. 1st 2017.
[38]Isotopic Abundances, IUPAC-CIAAW, accessed Jan. 7th 2017.
[39](1, 2, 3, 4) Atomic Masses, IUPAC-CIAAW, accessed Jan. 7th 2017.
[40]N.Stone, Table of Nuclear Magnetic Dipole and Electric Quadrupole Moments International Atomic Energy Agency, INDC(NDS)-0658, February 2014
[41]N.Stone, Table of Nuclear Quadrupole Moments, International Atomic Energy Agency, INDC(NDS)-650, December 2013
[42]Rahm, M., Hoffmann, R., & Ashcroft, N. W. (2016). Atomic and Ionic Radii of Elements 1-96. Chemistry - A European Journal, 22(41), 14625–14632. doi: 10.1002/chem.201602949
[43](1, 2) White, W. M. (2013). Geochemistry. Wiley. URL:
[44]Wikipedia. (2017). Goldschmidt classification — Wikipedia{,} The Free Encyclopedia. Retrieved April 30, 2017, from
[45](1, 2) Kyle & Laby Tables of Physical & Chemical constants. (2017). 3.7.5 Atomic radii. Retrieved April 30, 2017 from
[46]Pyykkö, P., & Atsumi, M. (2009). Molecular Double-Bond Covalent Radii for Elements Li-E112. Chemistry - A European Journal, 15(46), 12770–12779. doi:10.1002/chem.200901472
[47]Pyykkö, P., Riedel, S., & Patzschke, M. (2005). Triple-Bond Covalent Radii. Chemistry - A European Journal, 11(12), 3511–3520. doi:10.1002/chem.200401299


The package can be installed using pip

pip install mendeleev

You can also install the most recent version from the repository:

pip install

If you use conda you can install the package from my anaconda channel by

conda install -c lmmentel mendeleev=0.3.6


The simple interface to the data is through the element method that returns the Element objects:

>>> from mendeleev import element

The element method accepts unique identifiers: atomic number, atomic symbol or element’s name in english. To retrieve the entries on Silicon by symbol type

>>> si = element('Si')

Similarly to access the data by atomic number or element names type

>>> al = element(13)
>>> o = element('Oxygen')
>>> o.atomic_number

Lists of elements

The element method also accepts list or tuple of identifiers and then returns a list of Element objects

>>> c, h, o = element(['C', 'Hydrogen', 8])
('Carbon', 'Hydrogen', 'Oxygen')

Composite Attributes

Currently four of the attributes are more complex object than str, int or float, those are:

  • oxistates, returns a list of oxidation states
  • ionenergies, returns a dictionary of ionization energies
  • isotopes, returns a list of Isotope objects
  • ionic_radii returns a list of IonicRadius objects

Oxidation states

For examples oxistates returns a list of oxidation states for a given element

>>> fe = element('Fe')
>>> fe.oxistates
[6, 3, 2, 0, -2]

Ionization energies

The ionenergies returns a dictionary with ionization energies as values and degrees of ionization as keys.

>>> fe = element('Fe')
>>> fe.ionenergies
{1: 7.9024678,
 2: 16.1992,
 3: 30.651,
 4: 54.91,
 5: 75.0,
 6: 98.985,
 7: 125.0,
 8: 151.06,
 9: 233.6,
 10: 262.1,
 11: 290.9,
 12: 330.81,
 13: 361.0,
 14: 392.2,
 15: 456.2,
 16: 489.312,
 17: 1262.7,
 18: 1357.8,
 19: 1460.0,
 20: 1575.6,
 21: 1687.0,
 22: 1798.43,
 23: 1950.4,
 24: 2045.759,
 25: 8828.1875,
 26: 9277.681}


The isotopes attribute returns a list of Isotope objects with the following attributes per isotope

  • atomic_number
  • mass
  • abundance
  • mass_number
>>> fe = element('Fe')
>>> for iso in fe.isotopes:
...     print(iso)
 26   55.93494  91.75%    56
 26   56.93540   2.12%    57
 26   57.93328   0.28%    58
 26   53.93961   5.85%    54

The columns represent the attributes atomic_number, mass, abundance and mass_number respectively.

Ionic radii

Another composite attribute is ionic_radii which returns a list of IonicRadius object with the following attributes

  • atomic_number, atomic number of the ion
  • charge, charge of the ion
  • econf, electronic configuration of the ion
  • coordination, coordination type of the ion
  • spin, spin state of the ion (HS or LS)
  • crystal_radius
  • ionic_radius
  • origin, source of the data
  • most_reliable, recommended value
>>> fe = element('Fe')
>>> for ir in fe.ionic_radii:
...     print(ir)
charge=   2, coordination=IV   , crystal_radius= 0.770, ionic_radius= 0.630
charge=   2, coordination=IVSQ , crystal_radius= 0.780, ionic_radius= 0.640
charge=   2, coordination=VI   , crystal_radius= 0.750, ionic_radius= 0.610
charge=   2, coordination=VI   , crystal_radius= 0.920, ionic_radius= 0.780
charge=   2, coordination=VIII , crystal_radius= 1.060, ionic_radius= 0.920
charge=   3, coordination=IV   , crystal_radius= 0.630, ionic_radius= 0.490
charge=   3, coordination=V    , crystal_radius= 0.720, ionic_radius= 0.580
charge=   3, coordination=VI   , crystal_radius= 0.690, ionic_radius= 0.550
charge=   3, coordination=VI   , crystal_radius= 0.785, ionic_radius= 0.645
charge=   3, coordination=VIII , crystal_radius= 0.920, ionic_radius= 0.780
charge=   4, coordination=VI   , crystal_radius= 0.725, ionic_radius= 0.585
charge=   6, coordination=IV   , crystal_radius= 0.390, ionic_radius= 0.250

CLI utility

For those who work in the terminal there is a simple command line interface (CLI) for printing the information about a given element. The script name is and it accepts either the symbol or name of the element as an argument and prints the data about it. For example, to print the properties of silicon type

$ Si
   _  _  _  _      _
 _(_)(_)(_)(_)_   (_)
(_)          (_)_  _
(_)_  _  _  _  (_)(_)
  (_)(_)(_)(_)_   (_)
 _           (_)  (_)
(_)_  _  _  _(_)_ (_)
  (_)(_)(_)(_) (_)(_)(_)


  Metalloid element belonging to group 14 of the periodic table. It is
  the second most abundant element in the Earth's crust, making up 25.7%
  of it by weight. Chemically less reactive than carbon. First
  identified by Lavoisier in 1787 and first isolated in 1823 by


Atomic number                       14
Atomic radius                      132
Atomic volume                     12.1
Block                                p
Boiling point                     2628
Covalent radius 2008               111
Covalent radius 2009               116
Cpk color                      #daa520
Density                           2.33
Dipole polarizability            37.31
Electron affinity              1.38952
Electronic configuration  [Ne] 3s2 3p2
En allen                         11.33
En pauling                         1.9
Evaporation heat                   383
Fusion heat                       50.6
Gas basicity                     814.1
Group id                            14
Heat of formation                  450
Jmol color                     #f0c8a0
Lattice constant                  5.43
Lattice structure                  DIA
Mass                           28.0855
Melting point                     1683
Name                           Silicon
Period                               3
Proton affinity                    837
Series id                            5
Specific heat                    0.703
Symbol                              Si
Thermal conductivity               149
Vdw radius                         210


Documentation can be found here.


If you use mendeleev in a scientific publication, please consider citing the software as

L. M. Mentel, mendeleev - A Python resource for properties of chemical elements, ions and isotopes. , 2014– . Available at:

Here’s the reference in the BibLaTeX format

    author = {Mentel, Łukasz},
    title = {{mendeleev} -- A Python resource for properties of chemical elements, ions and isotopes},
    url = {},
    version = {0.3.6},
    date = {2014--},

or the older BibTeX format

   auhor = {Mentel, Łukasz},
   title = {mendeleev} -- A Python resource for properties of chemical elements, ions and isotopes, ver. 0.3.6},
   howpublished = {\url{}},
   year  = {2014--},


This project is supported by the RCN (The Research Council of Norway) project number 239193.

Release History

Release History

This version
History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


Download Files

Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
mendeleev-0.3.6-py2.py3-none-any.whl (194.7 kB) Copy SHA256 Checksum SHA256 py2.py3 Wheel Sep 17, 2017
mendeleev-0.3.6.tar.gz (218.9 kB) Copy SHA256 Checksum SHA256 Source Sep 17, 2017

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting