Here we take a simple approach to calculate the effective nuclear charge of a valence electron when only given the shell number. Remember, your shell number uses the variable N which stands for the principal quantum number.
Now here we have the atomic view of the aluminum atom. Aluminum is in Group 3A. It has an atomic number of 13. Here we say that it is 1 S 222S22P63S23P1 for its electron configuration.
Its effective nuclear charge formula, which is simply be effective nuclear charge which is Zef equals the atomic number of the element minus its shielding constant's. Now here the shielding constant can be seen as the inner core electrons for the given element.
So we use this simplified version of the effective nuclear charge when we only have the shell number.
