Table 2.
Coefficients/constants for calculating ionization energies of multielectron ions.
| Z | (1) | (2) | (3) | (4) |
|---|---|---|---|---|
| Screening constants | Coefficient a | Coefficient b | Reduced mass* | |
| B | 3 | 0.318 | 0.032 | 0.999939550 |
| C | 3.5 | 0.572 | 0.490 | 0.999954670 |
| N | 4 | 0.842 | 1.170 | 0.999961152 |
| O | 5 | 0.716 | 0.731 | 0.999966015 |
| F | 5.5 | 1.054 | 2.357 | 0.999971388 |
| Ne | 6 | 1.318 | 3.520 | 0.999972825 |
| Na | 7 | 2.222 | 11.809 | 0.999976377 |
| Mg | 7.5 | 2.344 | 12.925 | 0.999977367 |
| Al | 8.5 | 2.882 | 21.124 | 0.999979889 |
| Si | 9 | 3.012 | 22.521 | 0.999980614 |
| P | 9.5 | 3.194 | 24.599 | 0.999982497 |
| S | 10.5 | 2.850 | 22.194 | 0.999983051 |
| Cl | 11 | 2.968 | 23.026 | 0.999983571 |
| Ar | 11.5 | 3.306 | 27.683 | 0.999986454 |
|
| ||||
| ** | Screening constants | Coefficient a | Coefficient b | Reduced mass |
|
| ||||
| K | 11 | 2.968 | 23.026 | 0.999986113 |
| Ca | 11.5 | 3.306 | 27.683 | 0.999986467 |
| Sc | 13.5 | 3.366 | 30.828 | 0.999988489 |
| Ti | 14 | 3.832 | 38.481 | 0.999989186 |
| V | 14.5 | 4.542 | 51.618 | 0.999989405 |
| Cr | 15 | 5.138 | 62.763 | 0.999990000 |
| Mn | 15.5 | 5.658 | 73.472 | 0.999990188 |
| Fe | 16.5 | 5.850 | 82.119 | 0.999990702 |
| Co | 17 | 4.484 | 57.749 | 0.999990708 |
*Reduced masses are calculated from atomic number 5 to atomic number 26; for ions above atomic number 26, the reduced mass of atomic 26 is used since the differences between reduced masses at high atomic numbers are too small to show any differences in the calculated results.
**From the potassium series, the constants apply to calculating ionization energies from the third ionization energy (i.e., third ionization of potassium, fourth ionization of calcium, etc.).