Data

Elements

The followig data are currently available:

Name	Type	Comment	Unit	Data Source
abundance_crust	float	Abundance in the Earth’s crust	mg/kg	[21]
abundance_sea	float	Abundance in the seas	mg/L	[21]
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	[38]
atomic_volume	float	Atomic volume	cm3/mol
atomic_weight	float	Atomic weight[1]		[30][55]
atomic_weight_uncertainty	float	Atomic weight uncertainty[1]		[30][55]
block	int	Block in periodic table
boiling_point	float	Boiling temperature	K
c6	float	C_6 dispersion coefficient in a.u.	a.u.	[13][47]
c6_gb	float	C_6 dispersion coefficient in a.u. (Gould & Bučko)	a.u.	[20]
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	[36]
covalent_radius_pyykko_double	float	Double bond covalent radius by Pyykko et al.	pm	[35]
covalent_radius_pyykko_triple	float	Triple bond covalent radius by Pyykko et al.	pm	[37]
covalent_radius_slater	float	Covalent radius by Slater	pm	[44]
cpk_color	str	Element color in CPK convention	HEX	[52]
density	float	Density at 295K	g/cm3
description	str	Short description of the element
dipole_polarizability	float	Dipole polarizability	a.u.	[58]
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[3]	eV	[21][6]
electrons	int	Number of electrons
en_allen	float	Allen’s scale of electronegativity[4]	eV	[26][27]
en_ghosh	float	Ghosh’s scale of electronegativity		[18]
en_mulliken	float	Mulliken’s scale of electronegativity	eV	[31]
en_pauling	float	Pauling’s scale of electronegativity		[21]
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	[21]
geochemical_class	str	Geochemical classification		[50]
goldschmidt_class	str	Goldschmidt classification		[50][51]
group	int	Group in periodic table
heat_of_formation	float	Heat of formation	kJ/mol	[21]
ionenergy	tuple	Ionization energies	eV	[22]
ionic_radii	list	Ionic and crystal radii in pm	pm	[43]
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	[56]
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
mendeleev_number	int	Mendeleev’s number[5]		[34][48]
metallic_radius	float	Single-bond metallic radius	pm	[1]
metallic_radius_c12	float	Metallic radius with 12 nearest neighbors	pm	[1]
molcas_gv_color	str	Element color in MOCAS GV convention	HEX	[57]
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	[21]
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	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	[21]
vdw_radius_alvarez	float	Van der Waals radius according to Alvarez[7]	pm	[5][49]
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	[29]
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	[40]
vdw_radius_truhlar	float	Van der Waals radius according to Truhlar	pm	[28]
vdw_radius_uff	float	Van der Waals radius from the UFF	pm	[39]

Isotopes

Name	Type	Comment	Unit	Data Source
abundance	float	Relative Abundance		[54]
g_factor	float	Nuclear g-factor[8]		[46]
half_life	float	Half life of the isotope		[30]
half_life_unit	str	Unit in which the half life is given		[30]
is_radioactive	bool	Is the isotope radioactive		[53]
mass	float	Atomic mass	Da	[53]
mass_number	int	Mass number of the isotope		[53]
mass_uncertainty	float	Uncertainty of the atomic mass		[53]
spin	float	Nuclear spin quantum number
quadrupole_moment	float	Nuclear electric quadrupole moment[8]	b [100 fm^2]	[45]

Data Footnotes

[1]

(1, 2) Atomic Weights Atomic weights and their uncertainties were retrieved mainly from ref. [55]. For elements whose values were given as ranges the conventional atomic weights from Table 3 in ref. [30] 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 [21] 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 [25]. 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. [26] and [27] were taken as reported in eV without converting to Pauling units.

[5]	Mendeleev numbers Mendeleev numbers were mostly taken from [48] 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. [49].

[8]

(1, 2) Isotope g-factors and quadrupole moments The data regarding g-factors and electric quadrupole moments was parsed from easyspin webpage (accessed 25.01.2017) where additional notes are mentioned: Typo for Rh-103: Moment is factor of 10 too large 237Np, 239Pu, 243Am magnetic moment data from [21], section 11-2 In quadrupole moment data - a typo for Ac-227: sign should be +

Electronegativities

Since electronegativity is useful concept rather than a physical observable, several scales of electronegativity exist and some of them are available in mendeleev. Depending on the definition of a particular scale the values are either stored directly or recomputed on demand with appropriate formulas. The following scales are stored:

• Allen
• Ghosh
• Pauling

Moreover there are electronegativity scales that can be computed from their respective definition and the atomic properties available in mendeleev:

• Allred-Rochow
• Cottrell-Sutton
• Gordy
• Li and Xue
• Martynov and Batsanov
• Mulliken
• Nagle
• Sanderson

For a short overview on electronegativity see this presentation.

All the examples shown below are for Silicon:

>>> from mendeleev import element
>>> Si = element('Si')

Allen

The electronegativity scale proposed by Allen in ref [2] can be defined as:

\[\chi_{A} = \frac{\sum_{x} n_{x}\varepsilon_{x}}{\sum_{x}n_{x}}\]

where: \(\varepsilon_{x}\) is the multiplet-averaged one-electron energy of the subshell \(x\) and \(n_{x}\) is the number of electrons in subshell \(x\) and the summation runs over the valence shell.

The values that are tabulated were obtained from refs. [26] and [27].

Example:

>>> Si.en_allen
11.33
>>> Si.electronegativity('allen')
11.33

Allred and Rochow

The scale of Allred and Rochow [4] introduces the electronegativity as the electrostatic force exerted on the electron by the nuclear charge:

\[\chi_{AR} = \frac{e^{2}Z_{\text{eff}}}{r^{2}} \notag\]

where: \(Z_{\text{eff}}\) is the effective nuclear charge and \(r\) is the covalent radius.

Example:

>>> Si.electronegativity('allred-rochow')
0.00028240190249702736

Cottrell and Sutton

The scale proposed by Cottrell and Sutton [17] is derived from the equation:

\[\chi_{CS} = \sqrt{\frac{Z_{\text{eff}}}{r}}\]

where: \(Z_{\text{eff}}\) is the effective nuclear charge and \(r\) is the covalent radius.

Example:

>>> Si.electronegativity('cottrell-sutton')
0.18099342720014772

Ghosh

Ghosh [18] presented a scale of electronegativity based on the absolute radii of atoms computed as

\[\chi_{GH} = a \cdot (1/R) + b\]

where: \(R\) is the absolute atomic radius and \(a\) and \(b\) are empirical parameters.

Example:

>>> Si.en_ghosh
0.178503

Gordy

Gordy’s scale [19] is based on the potential that measures the work necessary to achieve the charge separation, according to:

\[\chi_{G} = \frac{eZ_{\text{eff}}}{r}\]

where: \(Z_{\text{eff}}\) is the effective nuclear charge and \(r\) is the covalent radius.

Example:

>>> Si.electronegativity('gordy')
0.03275862068965517

Li and Xue

Li and Xue [23][24] proposed a scale that takes into account different valence states and coordination environment of atoms and is calculated according to the following formula:

\[\chi_{LX} = \frac{n^{*}\sqrt{I_{j}/Ry}}{r}\]

where: \(n^{*}\) is the effective principal quantum number, \(I_{j}\) is the j’th ionization energy in eV, \(Ry\) is the Rydberg constant in eV and \(r\) is either the crystal radius or ionic radius.

Example:

>>> Si.en_li_xue(charge=4)
{u'IV': 13.16033405547733, u'VI': 9.748395596649873}
>>> Si.electronegativity('li-xue', charge=4)
{u'IV': 13.16033405547733, u'VI': 9.748395596649873}

Martynov and Batsanov

Martynov and Batsanov [7] used the square root of the averaged valence ionization energy as a measure of electronegativity:

\[\chi_{MB} = \sqrt{\frac{1}{n_{v}}\sum^{n_{v}}_{k=1} I_{k}}\]

where: \(n_{v}\) is the number of valence electrons and \(I_{k}\) is the \(k\) th ionization potential.

Example:

>>> Si.en_martynov_batsanov()
5.0777041564076963
>>> Si.electronegativity(scale='martynov-batsanov')
5.0777041564076963

Mulliken

Mulliken scale [31] is defined as the arithmetic average of the ionization potential (\(IP\)) and the electron affinity (\(EA\)):

\[\chi_{M} = \frac{IP + EA}{2}\]

Example:

>>> Si.en_mulliken()
4.0758415
>>> Si.electronegativity('mulliken')
4.0758415

Nagle

Nagle [32] derived his scale from the atomic dipole polarizability:

\[\chi_{N} = \sqrt[3]{\frac{n}{\alpha}} \notag\]

Example:

>>> Si.electronegativity('nagle')
0.47505611644667534

Pauling

Pauling’s thermochemical scale was introduced in [33] as a relative scale based on electronegativity differences:

\[\chi_{A} - \chi_{B} = \sqrt{E_{d}(AB) - \frac{1}{2}\left[E_{d}(AA) + E_{d}(BB)\right] }\]

where: \(E_{d}(XY)\) is the bond dissociation energy of a diatomic \(XY\). The values available in mendeleev are taken from ref. [21].

Example:

>>> Si.en_pauling
1.9
>>> Si.electronegativity('pauling')
1.9

Sanderson

Sanderson [41][42] established his scale of electronegativity based on the stability ratio:

\[\chi_{S} = \frac{\rho}{\rho_{\text{ng}}}\]

where: \(\rho\) is the average electron density \(\rho=\frac{Z}{4\pi r^{3}/3}\), and \(\rho_{\text{ng}}\) is the average electron density of a hypothetical noble gas atom with charge \(Z\).

Example:

>>> Si.en_sanderson()
0.3468157872145231
>>> Si.electronegativity()
0.3468157872145231

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