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_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_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]
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]
is_monoisotopic bool Is the element monoisotopic
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]
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_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]

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]
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

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:

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

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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