The part of the atom where electrons move is the what

C. Atom D has a Zeff of 6 and is therefore to the right of Atom E, which has a Zeff of 5.

Explanation:

Zeff means the effective nuclear charge and it is equal to the atomic number (number of protons) less the core electrons (all the electrons less the valence electrons).

Zeff=number of protons − number of core electrons