We’re being asked to **predict the effective nuclear charge (Z**_{eff}) for the outermost electrons in Rb atom based on the calculations for Na and K using Slaters rules

Recall that the *effective nuclear charge* is the force exerted by the nucleus onto an electron and is given by:

where **Z** = nuclear charge or atomic number and **S** = shielding constant.

The shielding constant can be calculated using *Slater’s Rules*:

__For __*ns* and *np* electrons:

1. Each electron in the *same group* will contribute **0.35** to the S value. A 1s electron contributes **0.30** to the S value of another 1s electron.

2. Each electron in the *n–1 group* contributes **0.85** to the S value.

3. Each electron in the *n–2 or greater group* contributes **1.00** to the S value.

__For __*nd* and *nf* electrons:

1. Each electron in the *same group* will contribute **0.35** to the S value.

2. Each electron in the *groups to the left* contributes **1.00** to the S value.

For this problem, we will determine the Z_{eff} for Na and K using the following steps:

*Step 1:* Determine the atomic number.

*Step 2:* Determine the electron configuration and group them by n-values.

*Step 3:* Calculate for the shielding constant using Slater's Rules.

*Step 4:* Calculate for Z_{eff}.

Then predict the Z_{eff} for Rb