Representative wave functions of Cu, ${\mathrm{Ir}}_{3}$Cr, and ${\mathrm{Zr}}_{3}$Al as determined from multiple-scattering $X\ensuremath{\alpha}$ cluster calculations are compared. While atomic parameters, specifically $s$-orbital electronegativities, predict an isotropic charge density for ${\mathrm{Ir}}_{3}$Cr and an anisotropic charge density for ${\mathrm{Zr}}_{3}$Al, quite different characteristics are observed. This is rationalized in terms of an effective $s$-orbital electronegativity which is sensitive to the local atomic environment. The actual charge density that results from these effective electronegativities correlates well with the observed mechanical properties, with the most isotropic charge density corresponding to the most ductile material.