Data

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

Elements

The following data are currently available:

Name	Type	Comment	Unit	Data Source
abundance_crust	float	Abundance in the Earth’s crust	mg/kg	[23]
abundance_sea	float	Abundance in the seas	mg/L	[23]
annotation	str	Annotations regarding the data
atomic_number	int	Atomic number
atomic_radius	float	Atomic radius	pm	[53]
atomic_radius_rahm	float	Atomic radius by Rahm et al.	pm	[45, 46]
atomic_volume	float	Atomic volume	cm3/mol
atomic_weight	float	Atomic weight(1)		[35, 63]
atomic_weight_uncertainty	float	Atomic weight uncertainty(1)		[35, 63]
block	str	Block in periodic table
boiling_point	float	Boiling temperature	K	[22]
c6	float	C_6 dispersion coefficient in a.u.	a.u.	[13, 56]
c6_gb	float	C_6 dispersion coefficient in a.u. (Gould & Bučko)	a.u.	[21]
cas	str	Chemical Abstracts Serice identifier
covalent_radius_bragg	float	Covalent radius by Bragg	pm	[10]
covalent_radius_cordero	float	Covalent radius by Cerdero et al.(2)	pm	[16]
covalent_radius_pyykko	float	Single bond covalent radius by Pyykko et al.	pm	[43]
covalent_radius_pyykko_double	float	Double bond covalent radius by Pyykko et al.	pm	[42]
covalent_radius_pyykko_triple	float	Triple bond covalent radius by Pyykko et al.	pm	[44]
cpk_color	str	Element color in CPK convention	HEX	[61]
critical_pressure	float	Critical pressure	MPa	[22]
critical_temperature	float	Critical temperature	K	[22]
density	float	Density at 295K(9)	g/cm3	[23, 66]
description	str	Short description of the element
dipole_polarizability	float	Dipole polarizability	a.u.	[51]
dipole_polarizability_unc	float	Dipole polarizability uncertainty	a.u.	[51]
discoverers	str	The discoverers of the element
discovery_location	str	The location where the element was discovered
discovery_year	int	The year the element was discovered
electron_affinity	float	Electron affinity(3)	eV	[6, 23]
electrons	int	Number of electrons
electrophilicity	float	Electrophilicity index	eV	[39]
en_allen	float	Allen’s scale of electronegativity(4)	eV	[31, 32]
en_ghosh	float	Ghosh’s scale of electronegativity		[18]
en_mulliken	float	Mulliken’s scale of electronegativity	eV	[36]
en_pauling	float	Pauling’s scale of electronegativity		[23]
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	[23]
geochemical_class	str	Geochemical classification		[59]
glawe_number	int	Glawe’s number (scale)		[19]
goldschmidt_class	str	Goldschmidt classification		[59, 60]
group	int	Group in periodic table
heat_of_formation	float	Heat of formation	kJ/mol	[23]
inchi	str	International Chemical Identifier		[24]
ionenergy	tuple	Ionization energies	eV	[26]
ionic_radii	list	Ionic and crystal radii in pm(8)	pm	[29, 52]
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	[64]
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	[22]
mendeleev_number	int	Mendeleev’s number(5)		[41, 57]
metallic_radius	float	Single-bond metallic radius	pm	[1]
metallic_radius_c12	float	Metallic radius with 12 nearest neighbors	pm	[1]
molar_heat_capacity	float	Molar heat capacity @ 25 C, 1 bar	J/(mol K)	[23]
molcas_gv_color	str	Element color in MOCAS GV convention	HEX	[65]
name	str	Name in English
name_origin	str	Origin of the name
neutrons	int	Number of neutrons (most abundant isotope)
oxistates	list	Commonly occurring oxidation states		[67]
nist_webbook_url	str	URL for the NIST Chemistry WebBook		[38]
oxistates	list	Oxidation states
period	int	Period in periodic table
pettifor_number	float	Pettifor scale		[41]
proton_affinity	float	Proton affinity	kJ/mol	[23]
protons	int	Number of protons
sconst	float	Nuclear charge screening constants(6)		[14, 15]
series	int	Index to chemical series
sources	str	Sources of the element
specific_heat_capacity	float	Specific heat capacity @ 25 C, 1 bar	J/(g K)	[23]
symbol	str	Chemical symbol
thermal_conductivity	float	Thermal conductivity @25 C	W/(m K)
triple_point_pressure	float	Triple point pressure	kPa	[22]
triple_point_temperature	float	Triple point temperature	K	[22]
uses	str	Applications of the element
vdw_radius	float	Van der Waals radius	pm	[23]
vdw_radius_alvarez	float	Van der Waals radius according to Alvarez(7)	pm	[5, 58]
vdw_radius_batsanov	float	Van der Waals radius according to Batsanov	pm	[8]
vdw_radius_bondi	float	Van der Waals radius according to Bondi	pm	[9]
vdw_radius_dreiding	float	Van der Waals radius from the DREIDING FF	pm	[34]
vdw_radius_mm3	float	Van der Waals radius from the MM3 FF	pm	[3]
vdw_radius_rt	float	Van der Waals radius according to Rowland and Taylor	pm	[48]
vdw_radius_truhlar	float	Van der Waals radius according to Truhlar	pm	[33]
vdw_radius_uff	float	Van der Waals radius from the UFF	pm	[47]

Isotopes

Name	Type	Comment	Unit	Data Source
abundance	float	Relative Abundance		[25]
abundance_uncertainty	float	Uncertainty of relative abundance		[25]
atomic_number	int	Atomic number
decay_modes	obj	Decay modes with intensities		[25]
discovery_year	int	Year the isotope was discovered		[25]
g_factor	float	Nuclear g-factor		[55]
g_factor_uncertainty	float	Uncertainty of the nuclear g-factor		[55]
half_life	float	Half life of the isotope		[25]
half_life_uncertainty	float	Uncertainty of the half life		[25]
half_life_unit	str	Unit in which the half life is given		[25]
is_radioactive	bool	Is the isotope radioactive		[62]
mass	float	Atomic mass	Da	[62]
mass_number	int	Mass number of the isotope		[62]
mass_uncertainty	float	Uncertainty of the atomic mass	Da	[62]
parity	str	Parity, if present, it can be either + or -		[25]
quadrupole_moment	float	Nuclear electric quadrupole moment	b [100 fm2]	[54]
quadrupole_moment_uncertainty	float	Nuclear electric quadrupole moment	b [100 fm2]	[54]
spin	str	Nuclear spin quantum number		[25]

Isotope Decay Modes

Name	Type	Comment	Unit	Data Source
isotope_id	int	ID of the isotope
mode	str	ASCII symbol of the decay mode		[25]
relation	str	Uncertainty of relative abundance		[25]
intensity	float	Intensity of the decay mode	%	[25]
is_allowed_not_observed	bool	If True decay mode is energetically allowed, but not experimentally observed		[25]
is_observed_intensity_unknown	bool	If True decay mode is observed, but its intensity is not experimentally known		[25]

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

Data Footnotes

1(1,2)

Atomic Weights

Atomic weights and their uncertainties were retrieved mainly from ref. [63]. For elements whose values were given as ranges the conventional atomic weights from Table 3 in ref. [35] 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 by Cordero et al.

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

Electron affinity

Electron affinities were taken from [23] 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 [30].

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

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

4

Allen’s configuration energies

The values of configurational energies from refs. [31] and [32] were taken as reported in eV without converting to Pauling units.

5

Mendeleev numbers

Mendeleev numbers were mostly taken from [57] 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.

6

Nuclear charge screening constants

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.

7

van der Waals radii according to Alvarez

The bulk of the radii data was taken from Ref. [5], but the radii for noble gasses were update according to the values in Ref. [58].

8

Ionic radii for Actinoid (III) ions

Ionic radii values for 3⁺ Actinoids were with coordination number 9 were taken from [29]. In addition crystal_radius values were computed by adding 14 pm to the ionic_radius values according to [52].

9

Densities

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 abundand are reported (for full list refer to [23]), 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 [66] 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