Question

why zinc is not a noble element? what is the criteria to be a noble element

Answer 1

Zinc has the following electronic configuration: ${1s}^2{2s}^2{2p}^6{3s}^2{3p}^6{4s}^2{3d}^{10}{4s}^2$

In contrast, the energy difference between the 4s, 3d, and 4p orbitals is rather minor for zinc. In addition to being close in energy, 4s and 4d also swap back and forth throughout the transition metals, which is how we know this for 4s and 3d.

Valence orbitals are thus defined in terms of the energy needed to fill them rather than their quantum numbers. Zinc does not qualify as a noble gas since its 4p orbitals count as valence (reactive) orbitals whereas its 4d orbitals do not.