# 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] is defined as:

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. [31] and [32].

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:

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:

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

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

Example:

```
>>> Si.en_ghosh
0.178503
```

## Gordy¶

Gordy’s scale [20] is based on the potential that measures the work necessary to achieve the charge separation, according to:

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 [27, 28] proposed a scale that takes into account different valence states and coordination environment of atoms and is calculated according to the following formula:

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:

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

Example:

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

## Nagle¶

Nagle [37] derived his scale from the atomic dipole polarizability:

Example:

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

## Pauling¶

Pauling’s thermochemical scale was introduced in [40] as a relative scale based on electronegativity differences:

where: \(E_{d}(XY)\) is the bond dissociation energy of a diatomic \(XY\). The values available in mendeleev are taken from ref. [23].

Example:

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

## Sanderson¶

Sanderson [49, 50] established his scale of electronegativity based on the stability ratio:

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
```

## Fetching all electronegativities¶

If you want to fetch all the available scales for all elements you can use the
`fetch_electronegativities`

function,
that collect all the values into a `DataFrame`

.