Electronegativity of Potassium (Pauling)

Question

Just a little question, I was taught that the electronegativity of potassium[K] is 1, but I recently discovered most internet resources say 0.82. Some even say both. What is the actual electronegativity of potassium, 0.82 or 1?

Answer 1

It depends which electronegativity scale you choose to use. There are a lot of different scales for comparing electronegativities of the elements. I've included a list of 11 of them below if you're interested. In any case here are the electronegativities reported for potassium using 5 different electronegativity scales. All values are in "Pauling units" so that the numbers can be compared. The Pauling scale is the most commonly used, so 0.82 would be a reasonable estimate for the electronegativity of potassium.

• Pauling 0.82
• Sanderson 0.45
• Allred Rochow 0.91
• Mulliken-Jaffe 0.73
• Allen 0.734

On the Pauling scale, electronegativities range from around 0.7 to 3.98 (fluorine), so as expected, potassium is at the electropositive end. None of these scales report a value of 1.

List of 11 Different Electronegativity Scales

• Pauling Scale: (1932) Obtains values by thermochemical methods

• Mulliken Relation: (1934) Defines a relation that depends upon the orbital characteristics of an atom in a molecule. Mulliken electronegativity is the numerical average of the ionisation potential and electron affinity

• Gordy Scale: (1946) Defines electronegativity in terms of the
  effective nuclear charge and the covalent radius. (Zeff)e/r

• Walsh Scale: (1951) Relates electronegativity to stretching force
  constants of the bonds of an atom to a hydrogen atom.
• Huggins Scale: (1953) Alternative to Pauling's thermochemical
  procedure
• Sanderson Scale: (1955) The ratio of the average electron density of an atom to that of a hypothetical "inert" atom having the same number of electrons. This ratio is a measure of the relative compactness of the atom
• Allred-Rochow Scale: (1958) Defines electronegativity in terms of the effective nuclear charge and covalent radius. Like the Gordy scale but uses (Zeff)e/r2
• Jaffe Scale: (1962) Uses the electronegativity of orbitals rather
  than atoms to develop group electronegativities for molecular fragments (e.g. $\ce{CH3}$ vs $\ce{CF3}$) that take into account the charge of a group, the effects of substituents, and the hybridization of the bonding orbital
• Phillips Scale: (1968) Defines electronegativity in terms of the
  dielectric properties of atoms in a given valence state
• Martynov & Batsanov Scale: (1980) Obtained by averaging the
  successive ionisation energies of an element's valence electrons
• Allen CE Scale: (1992) Configuration energy (CE), the average
  one-electron valence shell energy of the ground-state free atom, is
  used to quantify metal-covalent-ionic bonding