We consider all s2 − sp and ss − sp transitions which are thought to be free of serious configuration interactions for the following species: Mg I , Al II , Si III , P IV , Ca I , Zn I , Ga II , Ge III , As IV , Sr I , Cd I , In II , Sn III , Ba I , Hg I , Tl II , Pb III . Oscillator strengths are calculated from intermediate coupling and scaled Thomas–Fermi–Dirac wavefunctions. Comparison with experimental measurements for the s2 – sp transitions shows good agreement. A general trend with atomic weight is probably due to neglect of complete allowance for relativistic effects.