A series of four new analogue phases Ca₂M₂X (M = Pd, Pt and X = Al, Ge) were prepared by direct combination of the respective elements in stoichiometric mixtures at high temperature in order to analyze the impact of valence electron count (vec) and electronegativity differences (Δχ) on the structure selection and stability. Their crystal structures, as determined from single-crystal X-ray diffraction data, correspond to two different but closely related structure types. The first compound, Ca₂Pd₂Ge (I), is an unprecedented ternary ordered variant of the Zr₂Al₃-type (orthorhombic, Fdd2). The three other phases, Ca₂Pt₂Ge (II), Ca₂Pd₂Al (III) and Ca₂Pt₂Al (IV), adopt the Gd₂Ge₂Al-type structure (monoclinic, C2/c). All title structures feature linear chains of the noble metals (Pd or Pt). The Pd linear chains in I are undistorted with equidistant Pd···Pd atoms, whereas the metal chains in II–IV are pairwise distorted, resulting in short connected {Pd₂} or {Pt₂} dumbbells that are separated by longer M···M contacts. The occurrence and magnitude of the pairing distortion in these chains are controlled by the vec and the Δχ between the constituent elements, a result which is supported by analysis of the calculated Bader effective charges. The metal chains act as charge modulation units, critical for the stability and the electronic flexibility of the structures by an adequate adjustment of the metal–metal bond order to both the vec and the degree of charge transfer. Thus, Ca₂Pd₂Ge (28 ve/f.u) is a Zintl-like, charge optimized phase with formally zerovalent Pd atoms forming the undistorted metal chains; semimetallic properties are predicted by TB-LMTO calculations. In contrast, the isoelectronic Ca₂Pt₂Ge is predicted to be a good metal with the Fermi level located at a local maximum of the DOS, a fingerprint of potential electronic instability. This is due to greater charge transfer to the more electronegative Pt atoms forming the metal chains and probably to packing frustration in the well packed structure that may prevent a larger distortion of the Pt chains. However, the instability is suppressed in the aliovalent but isostructural phases Ca₂M₂Al (27 ve/f.u) with an enhancement of the pairing distortion within the metal chains but lower M–M bond order. Further reduction of the vec as in Ca₂M₂Cd (26 ve/f.u) may induce a transition toward the more geometrically flexible W₂CoB₂-type with a low dimensional structure, to create more room for a larger distortion of the metal chain as dictated by the shortage of valence electrons.