See also: Electronegativities of the elements (data page)There are no reliable sources for Pm, Eu and Yb other than the range of 1.1–1.2; see Pauling, Linus (1960).
3rd ed., Cornell University Press, p. 93.Section names here refer to the abbreviation in the table.
As quoted at http://www.webelements.com/ from these sources: As quoted from these sources in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition.
Boca Raton, Florida, 2003; Section 9, Molecular Structure and Spectroscopy; Electronegativity As quoted from these sources in: J.A.
Dean (ed), Lange's Handbook of Chemistry (15th Edition), McGraw-Hill, 1999; Section 4; Table 4.5, Electronegativities of the Elements.