# Chapter 7 - Periodic Properties of the Elements - Exercises: 7.13a

Effective nuclear charge $(Z_{eff})$ is a representation of an average of the electrical field experienced by a single electron, which is the average of the attraction between that electron and the nucleus and the repulsions between that electron and other electrons.

#### Work Step by Step

As we have witnessed in Chapter 6, an electron in a many-electron atom does not just experience the simple attraction between the nucleus and the electron, but also experience the electron-electron repulsions among the electrons. Therefore, effective nuclear charge $(Z_{eff})$ is created to account for this problem. It is a representation of an average of the electrical field experienced by a single electron, which is the average of the attraction between that electron and the nucleus and the repulsions between that electron and other electrons. $Z_{eff}$ is calculated most simply according to the following formula $$Z_{eff}=Z-S$$ where $Z$ is the nuclear charge of the element and $S$ is the screening constant (the electron-electron repulsions that reduce the attraction between the nucleus and the electron).

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.