Electronegativity of Potassium (Pauling)

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

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