• alkali metals;
  • ammonium;
  • computational chemistry;
  • electronegativity;
  • ion pairs
Thumbnail image of graphical abstract

The computational electronegativity of the ammonium radical reveals the differences between atoms and “pseudo-atoms” in a paper from A. Whiteside, S. S. Xantheas, and M. Gutowski on page 13197 ff. It is shown from simulations and experimental data that NH4 can behave like an alkali metal if its molecular properties are suppressed. Activating these properties, such as geometric flexibility, exposes their influence upon the pseudo-atom's behaviour. Four of the leading historical figures in this area of chemistry are depicted: clockwise from top left: J. J. Berzelius, R. S. Mulliken, G. Herzberg, and L. C. Pauling. Portrait credits: Berzelius from Wikimedia Commons, Mulliken and Pauling from G. Hund, Herzberg from University of Saskatchewan Archives (A-3234).