Question

what is epsilon zero for chemistry?

Answer 1

The electric constant,
i.e. permittivity of a vaccum \[\varepsilon_o^{}=\frac1{\mu_o^{} c_o^2}=\frac{e^2}{2\alpha h c_o^{}}\approx8.854\times10^{-12}\left[\frac{\text{C}^2}{\text{N m}^2 }\right]\]