An alternative scale of electromagnetically to that of Pauling was proposed by Robert Mulliken, who argued that an electronegative atom was likely to have both a high ionization energy, as it would not readily lose electrons, and a high negative electron gain energy, as it would be energetically favourable for it to gain electrons. Mulliken defined electronegativity as an average of these terms, as shown below.
$$
\chi^{\mathrm{M}}=\frac{1}{2}\left(I_{1}-E_{\mathrm{og} 1}\right)
$$
Use the data in Figures $3.35$ (p.156) and $3.38(\mathrm{p} .158)$ to calculate $\chi_{M}$ for the Group 17 elements, and comment on the trend observed.