Question

effective nuclear charge, z_{eff}, is defined as
answer:
the number of protons minus the number
of valence electrons.
the difference in electronegativities of
two bonded atoms or ions.
the number of protons minus the number
of electrons.
the true nuclear charge minus the charge
that is shielded by electrons.
the number of protons in the nucleus.

Explanation:

Effective nuclear charge \(Z_{eff}\) is calculated as the true nuclear charge (number of protons) minus the charge shielded by electrons (electron - electron repulsion effect). Option A is incorrect as it's not protons minus valence electrons. Option B is about electronegativity difference, not \(Z_{eff}\). Option C is the formula for net charge of an ion (not \(Z_{eff}\)). Option E is just the number of protons (nuclear charge, not effective).

Answer:

D. the true nuclear charge minus the charge that is shielded by electrons.