Data

To find out how to fetch data in bulk, check out the documentation about data access.

Elements

Class: Element

The following data are currently available:

Attribute name	Description	Unit	Value origin	Citation keys
abundance_crust	Abundance in the Earth’s crust	mg/kg	stored	[25]
abundance_sea	Abundance in the seas	mg/L	stored	[25]
atomic_number	Atomic number		stored
atomic_radius_rahm	Atomic radius by Rahm et al.	pm	stored	[51, 52]
atomic_radius	Atomic radius	pm	stored	[59]
atomic_volume	Atomic volume	cm^3/mol	computed
atomic_weight_uncertainty	Atomic weight uncertainty	Da	stored	[39, 73]
atomic_weight	Relative atomic weight ([1])	Da	stored	[39, 73]
block	Block in periodic table		stored
boiling_point	Boiling point	K	stored	[24]
c6_gb	C_6 dispersion coefficient according to Gould & Bučko	hartree/bohr^6	stored	[22]
c6	C_6 dispersion coefficient	hartree/bohr^6	stored	[13, 64]
cas	Chemical Abstracts Serice identifier		stored
covalent_radius_bragg	Covalent radius by Bragg	pm	stored	[10]
covalent_radius_cordero	Covalent radius by Cerdero et al. ([2])	pm	stored	[16]
covalent_radius_pyykko_double	Double bond covalent radius by Pyykko et al.	pm	stored	[48]
covalent_radius_pyykko_triple	Triple bond covalent radius by Pyykko et al.	pm	stored	[50]
covalent_radius_pyykko	Single bond covalent radius by Pyykko et al.	pm	stored	[49]
cpk_color	Element color in CPK convention as HEX codes.		stored	[70]
critical_pressure	Critical pressure	MPa	stored	[24]
critical_temperature	Critical temperature	K	stored	[24]
density	Density at 295K ([3])	g/cm^3	stored	[25, 77]
description	Short description of the element		stored
dipole_polarizability_unc	Uncertainty of the dipole polarizability	bohr^3	stored	[76]
dipole_polarizability	Dipole polarizability	bohr^3	stored	[76]
discoverers	The discoverers of the element		stored
discovery_location	The location where the element was discovered		stored
discovery_year	The year the element was discovered		stored
econf	Ground state electronic configuration		stored
electron_affinity	Electron affinity ([4])	eV	stored	[6, 25]
electronegativity_allen	Allen’s scale of electronegativity ([5])	eV	stored	[35, 36]
electronegativity_allred_rochow	Allred and Rochow’s scale of electronegativity	e^2/pm^2	computed	[4]
electronegativity_cottrell_sutton	Cottrell and Sutton’s scale of electronegativity	e^0.5/pm^0.5	computed	[17]
electronegativity_ghosh	Ghosh’s scale of electronegativity	1/pm	stored	[19]
electronegativity_gordy	Gordy’s scale of electronegativity	e/pm	computed	[21]
electronegativity_li_xue	Li and Xue’s scale of electronegativity	1/pm	computed	[31, 32]
electronegativity_martynov_batsanov	Martynov and Batsanov’s scale of electronegativity	eV^0.5	computed	[7]
electronegativity_mulliken	Mulliken’s scale of electronegativity	eV	computed	[41]
electronegativity_nagle	Nagle’s scale of electronegativity	1/bohr	computed	[42]
electronegativity_pauling	Pauling’s scale of electronegativity		stored	[25]
electronegativity_sanderson	Sanderson’s scale of electronegativity		computed	[56, 57]
electrons	Number of electrons		computed
electrophilicity	Parr’s electrophilicity index		computed	[45]
en_gunnarsson_lundqvist	Gunnarsson-Lundqvist’s scale of electronegativity	eV	stored	[23, 54]
en_miedema	Miedema’s scale of Electronegativity	V	stored	[18, 71]
en_mullay	Mullay’s scale of electronegativity ([6])		stored	[40]
en_robles_bartolotti	Robles-Bartolotti’s scale of electronegativity	eV	stored	[54]
evaporation_heat	Evaporation heat ([8])	kJ/mol	stored
fusion_heat	Fusion heat ([11])	kJ/mol	stored
gas_basicity	Gas basicity	kJ/mol	stored	[25]
geochemical_class	Geochemical classification		stored	[68]
glawe_number	Glawe’s number (scale)		stored	[20]
goldschmidt_class	Goldschmidt classification		stored	[68, 69]
group	Group in the periodic table		stored
hardness	Absolute hardness. Can also be calcualted for ions.	eV	computed	[44]
heat_of_formation	Heat of formation	kJ/mol	stored	[25]
inchi	International Chemical Identifier		computed	[26]
ionenergy	See IonizationEnergy class documentation		stored	[30]
ionic_radii	See IonicRadius class documentation		stored	[33, 58]
is_monoisotopic	Is the element monoisotopic		stored
is_radioactive	Is the element radioactive		stored
isotopes	See Isotope class documentation		stored
jmol_color	Element color in Jmol convention as HEX codes.		stored	[74]
lattice_constant	Lattice constant	angstrom	stored
lattice_structure	Lattice structure code		stored
mass_number	Mass number of the most abundant isotope		computed
melting_point	Melting point at 101.325 kPa pressure	K	stored	[24]
mendeleev_number	Mendeleev’s number ([15])		stored	[47, 66]
metallic_radius_c12	Metallic radius with 12 nearest neighbors	pm	stored	[1]
metallic_radius	Single-bond metallic radius	pm	stored	[1]
miedema_electron_density	Electron density parameter from a model by Miedema		stored	[18, 71]
miedema_molar_volume	Molar volume parameter from a model by Miedema	cm^3	stored	[18, 71]
molar_heat_capacity	Molar heat capacity @ 25 C, 1 bar	J/mol/K	stored	[25]
molcas_gv_color	Element color in MOCAS GV convention as HEX codes.		stored	[75]
name_origin	Origin of the name		stored
name	Name in English		stored
neutrons	Number of neutrons		computed
nist_webbook_url	URL for the NIST Chemistry WebBook		computed	[43]
nvalence	Number of valence electrons		computed
oxides	Possible oxides based on oxidation numbers		computed
oxistates	See OxidationState class documentation		stored	[78]
period	Period in periodic table		stored
pettifor_number	Pettifor scale		stored	[47]
political_stability_of_top_producer	A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.		stored	[65]
political_stability_of_top_reserve_holder	A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.		stored	[65]
price_per_kg	Price per kg in USD ([16])	USD/kg	stored	[79]
production_concentration	The percentage of an element produced in the top producing country. The higher the value, the larger risk there is to supply.	%	stored	[65]
proton_affinity	Proton affinity	kJ/mol	stored	[25]
protons	Number of protons		computed
recycling_rate	The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply.	%	stored	[65]
relative_supply_risk	An integrated supply risk index from 1 (very low risk) to 10 (very high risk). This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores.		stored	[65]
reserve_distribution	The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply.	%	stored	[65]
sconst	See ScreeningConstant class documentation ([18])		stored	[14, 15]
series	Series in the periodic table		stored
softness	Absolute softness. Can also be calculated for ions.	1/eV	computed
sources	Sources of the element		stored
specific_heat_capacity	Specific heat capacity @ 25 C, 1 bar	J/g/K	stored	[25]
substitutability	The availability of suitable substitutes for a given commodity. High - substitution not possible or very difficult, medium - substitution is possible but there may be an economic and/or performance impact, low = substitution is possible with little or no economic and/or performance impact		stored	[65]
symbol	Chemical symbol		stored
thermal_conductivity	Thermal conductivity @25 C	W/m/K	stored
top_3_producers	Top 3 countries or regions that produce the element.		stored	[65]
top_3_reserve_holders	Top 3 countries or regions that hold reserves the element.		stored	[65]
triple_point_pressure	Presseure of the triple point	kPa	stored	[24]
triple_point_temperature	Temperature of the triple point	K	stored	[24]
uses	Main applications of the element		stored
vdw_radius_alvarez	Van der Waals radius according to Alvarez ([19])	pm	stored	[5, 67]
vdw_radius_batsanov	Van der Waals radius according to Batsanov	pm	stored	[8]
vdw_radius_bondi	Van der Waals radius according to Bondi	pm	stored	[9]
vdw_radius_dreiding	Van der Waals radius from the DREIDING FF	pm	stored	[38]
vdw_radius_mm3	Van der Waals radius from the MM3 FF	pm	stored	[3]
vdw_radius_rt	Van der Waals radius according to Rowland and Taylor	pm	stored	[55]
vdw_radius_truhlar	Van der Waals radius according to Truhlar	pm	stored	[37]
vdw_radius_uff	Van der Waals radius from the UFF	pm	stored	[53]
vdw_radius	Van der Waals radius	pm	stored	[25]
zeff	Effective nuclear charge		computed

Isotopes

Class: Isotope

Attribute name	Description	Unit	Value origin	Citation keys
abundance_uncertainty	Uncertainty of relative abundance		stored	[29]
abundance	Relative Abundance		stored	[29]
atomic_number	Atomic number		stored
decay_modes	Decay modes with intensities		stored	[29]
discovery_year	Year the isotope was discovered		stored	[29]
g_factor_uncertainty	Uncertainty of the nuclear g-factor		stored	[61, 62]
g_factor	Nuclear g-factor ([12])		stored	[61, 62]
half_life_uncertainty	Uncertainty of the half life		stored	[29]
half_life_unit	Unit in which the half life is given ([13])		stored	[29]
half_life	Half life of the isotope		stored	[29]
is_radioactive	Is the isotope radioactive		stored	[72]
mass_number	Mass number of the isotope		stored	[72]
mass_uncertainty	Uncertainty of the atomic mass	Da	stored	[72]
mass	Atomic mass	Da	stored	[72]
parity	Parity, if present, it can be either + or -		stored	[29]
quadrupole_moment_uncertainty	Nuclear electric quadrupole moment uncertainty	100 fm^2	stored	[60, 63]
quadrupole_moment	Nuclear electric quadrupole moment ([17])	100 fm^2	stored	[60, 63]
spin	Nuclear spin quantum number		stored	[29]

Isotope Decay Modes

Class: IsotopeDecayMode

Attribute name	Description	Unit	Value origin	Citation keys
intensity	Intensity of the decay mode		stored	[29]
is_allowed_not_observed	If True decay mode is energetically allowed, but not experimentally observed		stored	[29]
is_observed_intensity_unknown	If True decay mode is observed, but its intensity is not experimentally known		stored	[29]
isotope_id	ID of the isotope, links to the isotopes table.		stored	[29]
mode	ASCII symbol of the decay mode		stored	[29]
relation	Uncertainty of relative abundance		stored	[29]

The different modes in the table are stores as ASCII representations for compatibility. The table below provides explanations of the symbols.

ASCII	Unicode	Description
A	\(\alpha\)	\(\alpha\) emission
p	p	proton emission
2p	2p	2-proton emission
n	n	neutron emission
2n	2n	2-neutron emission
EC	\(\epsilon\)	electron capture
e+	\(e^{+}\)	positron emission
B+	\(\beta^{+}\)	\(\beta^{+}\) decay (\(\beta^{+}=\epsilon+e^{+}\))
B-	\(\beta^{-}\)	\(\beta^{-}\) decay
2B-	2\(\beta^{-}\)	double \(\beta^{-}\) decay
2B+	2\(\beta^{+}\)	double \(\beta^{+}\) decay
B-n	\(\beta^{-}\) n	\(\beta^{-}\)-delayed neutron emission
B-2n	\(\beta^{-}\) 2n	\(\beta^{-}\)-delayed 2-neutron emission
B-3n	\(\beta^{-}\) 3n	\(\beta^{-}\)-delayed 3-neutron emission
B+p	\(\beta^{+}\) p	\(\beta^{+}\)-delayed proton emission
B+2p	\(\beta^{+}\) 2p	\(\beta^{+}\)-delayed 2-proton emission
B+3p	\(\beta^{+}\) 3p	\(\beta^{+}\)-delayed 3-proton emission
B-A	\(\beta^{-}\alpha\)	\(\beta^{-}\)-delayed \(\alpha\) emission
B+A	\(\beta^{+}\alpha\)	\(\beta^{+}\)-delayed \(\alpha\) emission
B-d	\(\beta^{-}\) d	\(\beta^{-}\)-delayed deuteron emission
B-t	\(\beta^{-}\) t	\(\beta^{-}\)-delayed triton emission
IT	IT	internal transition
SF	SF	spontaneous fission
B+SF	\(\beta^{+}\) SF	\(\beta^{+}\)-delayed fission
B-SF	\(\beta^{-}\) SF	\(\beta^{-}\)-delayed fission
24Ne	24Ne	heavy cluster emission

Atomic Scattering Factors

Class: ScatteringFactor

Attribute name	Description	Unit	Value origin	Citation keys
atomic_number	Atomic number		stored	[27, 28]
energy	Energy of the incident photon ([7])	eV	stored	[27, 28]
f1	Scattering factor f1 ([9])		stored	[27, 28]
f2	Scattering factor f2 ([10])		stored	[27, 28]

Ionization Energies

Class: IonizationEnergy

Attribute name	Description	Unit	Value origin	Citation keys
atomic_number	Atomic number of the element		stored
ground_configuration	Ground state electronic configuration		stored
ground_level	Term symbol and J value for the largest component in the ground level		stored
ground_shells	Ground state shells		stored
ion_charge	Charge of the ion (degree of ionization relative to neutral atom)		stored
ionization_energy	Ionization energy in eV	eV	stored
ionized_level	Configuration, term, and J value of the next ionized state		stored
is_semi_empirical	Flag for semi-empirical determination of the ionization energy		stored
is_theoretical	Flag for theoretical determination of the ionization energy		stored
isoelectonic_sequence	Isoelectronic sequence of the species		stored
references	References related to the ionization energies		stored
species_name	Name of the species		stored
uncertainty	Uncertainty in the ionization energy measurement	eV	stored

Ionic Radii

Class: IonicRadius

Attribute name	Description	Unit	Value origin	Citation keys
atomic_number	Atomic number		stored	[58]
charge	Charge of the ion		stored	[33, 58]
coordination	Type of coordination		stored	[33, 58]
crystal_radius	Crystal radius	pm	stored	[33, 58]
econf	Electronic configuration of the ion		stored	[33, 58]
ionic_radius	Ionic radius	pm	stored	[33, 58]
most_reliable	Most reliable value (see reference)		stored	[58]
origin	Source of the data		stored	[58]
spin	Spin state: HS: high spin, LS: low spin		stored	[33, 58]

Notes

Ionic radii for Actinoid (III) ions

Ionic radii values for 3⁺ Actinoids were with coordination number 9 were taken from [33]. In addition, crystal_radius values were computed by adding 14 pm to the ionic_radius values according to [58].

Oxidation States

Class: OxidationState

Attribute name	Description	Unit	Value origin	Citation keys
atomic_number	Atomic number		stored	[78]
category	Either main or extended flag to indicate the type of oxidation state		stored	[78]
oxidation_state	Oxidation state		stored	[78]

Phase Transitions

Class: PhaseTransition

Attribute name	Description	Unit	Value origin	Citation keys
allotrope	Allotrope name		stored	[24]
atomic_number	Atomic number		stored
boiling_point	Boiling point	K	stored	[24]
critical_pressure	Critical pressure	MPa	stored	[24]
critical_temperature	Critical temperature	K	stored	[24]
is_sublimation_point	Indicates that boiling_point marks a sublimation point, where the vapor pressure of the solid phase reaches 101.325 kPa (1 atm)		stored	[24]
is_transition	Indicates that melting_point marks the temperature of the transition to the crystalline form immediately below that entry		stored	[24]
melting_point	Melting point at 101.325 kPa pressure ([14])	K	stored	[24]
triple_point_pressure	Pressure in kPa of the triple point	kPa	stored	[24]
triple_point_temperature	Temperature in K of the triple point	K	stored	[24]

Screening Constants

Class: ScreeningConstant

Attribute name	Description	Unit	Value origin	Citation keys
atomic_number	Atomic number		stored	[14, 15]
n	Principal quantum number		stored	[14, 15]
s	Subshell label, (s, p, d, …)		stored	[14, 15]
screening	Screening constant		stored	[14, 15]

Data Footnotes

[1]

atomic_weight

Atomic weights and their uncertainties were retrieved mainly from ref. [73]. For elements whose values were given as ranges the conventional atomic weights from Table 3 in ref. [39] were taken. For radioactive elements the standard approach was adopted where the weight is taken as the mass number of the most stable isotope. The data was obtained from CIAAW page on radioactive elements. In cases where two isotopes were specified the one with the smaller standard deviation was chosen. In case of Tc and Pm relative weights of their isotopes were used, for Tc isotope 98, and for Pm isotope 145 were taken from CIAAW.

[2]

covalent_radius_cordero

In order to have a more homogeneous data for covalent radii taken from ref. [16] the values for 3 different valences for C, also the low and high spin values for Mn, Fe Co, were respectively averaged.

[3]

density

Density values for solids and liquids are always in units of grams per cubic centimeter and can be assumed to refer to temperatures near room temperature unless otherwise stated. Values for gases are the calculated ideal gas densities at 25°C and 101.325 kPa.

Original values for gasses are converted from g/L to g/cm³.

For elements where several allotropes exist, the density corresponding to the most abundant are reported (for full list refer to [25]), namely:

• Antimony (gray)

• Berkelium (α form)

• Carbon (graphite)

• Phosphorus (white)

• Selenium (gray)

• Sulfur (rhombic)

• Tin (white)

For elements where experimental data is not available, theoretical estimates taken from [77] are used, namely for:

• Astatine

• Francium

• Einsteinium

• Fermium

• Mendelevium

• Nobelium

• Lawrencium

• Rutherfordium

• Dubnium

• Seaborgium

• Bohrium

• Hassium

• Meitnerium

• Darmstadtium

• Roentgenium

• Copernicium

• Nihonium

• Flerovium

• Moscovium

• Livermorium

• Tennessine

• Oganesson

[4]

electron_affinity

Electron affinities were taken from [25] for the elements for which the data was available. For He, Be, N, Ar and Xe affinities were taken from [6] where they were specified for metastable ions and therefore the values are negative.

Updates

• Electron affinity of niobium was taken from [34].

• Electron affinity of cobalt was taken from [11].

• Electron affinity of lead was taken from [12].

[5]

electronegativity_allen

The values of configurational energies from refs. [35] and [36] were taken as reported in eV without converting to Pauling units.

[6]

en_mullay

In the original paper multiple values of electronegativity are provided for several elements. The values corresponding to following hybrids were chosen:

• C sp3

• N p

• O p

• F p

• CL p

• Br p

• I p

[7]

energy

specific data references available at cited data source

[8]

evaporation_heat

• H: evaporation heat of H-H

• F: evaporation heat of F-F

• Cl: evaporation heat of Cl-Cl

• Br: evaporation heat of Br-Br

• I: evaporation heat of I-I

[9]

f1

specific data references available at cited data source

[10]

f2

specific data references available at cited data source

[11]

fusion_heat

• H: fusion heat of H-H

• F: fusion heat of F-F

• Cl: fusion heat of Cl-Cl

• Br: fusion heat of Br-Br

• I: fusion heat of I-I

[12]

g_factor

Original data taken from [61] and updated with the data from [62] for all ground state isotopes.

[13]

half_life_unit

1 year = 365.2422 days = 31 556 926 sec

[14]

melting_point

Melting points for carbon from the original source are not included since they are not at standard pressure

[15]

mendeleev_number

Mendeleev numbers were sourced from [66] but the range was extended to cover the whole periodic table following the prescription in the article of increasing the numbers going from top to bottom in each group and group by group from left to right in the periodic table.

[16]

price_per_kg

In cases where a range was provided in the source, the lower value was used. In cases of multiple isotopes the lower priced isotope’s price was used.

[17]

quadrupole_moment

Original data taken from [60] and updated with the data from [63] for all ground state isotopes.

[18]

sconst

The screening constants were calculated according to the following formula

\[\sigma_{n,l,m} = Z - n\cdot\zeta_{n,l,m}\]

where \(n\) is the principal quantum number, \(Z\) is the atomic number, \(\sigma_{n,l,m}\) is the screening constant, \(\zeta_{n,l,m}\) is the optimized exponent from [14, 15].

For elements Nb, Mo, Ru, Rh, Pd and Ag the exponent values corresponding to the ground state electronic configuration were taken (entries with superscript a in Table II in [15]).

For elements La, Pr, Nd and Pm two exponent were reported for 4f shell denoted 4f and 4f’ in [15]. The value corresponding to 4f were used since according to the authors these are the dominant ones.

[19]

vdw_radius_alvarez

The bulk of the radii data was taken from Ref. [5], but the radii for noble gasses were updated according to the values in Ref. [67].