Answer:
Both Nickel (Ni, 28, 58.69) and Technetium (Tc, 43, [98]) have these features in common:
- transition metals
- some gray color (Tc is silver)
- are in the d block
- have two electrons in valence shell (although Tc's valence is 6)
- very similar electronegativity levels (1.9 vs 1.91)
- don't have a refractive index
- don't have a critical temperature
- don't have a heat of combustion measurement
- don't have an EU Number or NFPA hazard level
- don't have an autoignition point or a flashpoint
