An analytical chemist is classifying a series of alkaline earth metals. A reference table of several Group 2 elements is shown below:
| Group 2 element | Atomic number | Relative atomic mass |
|---|---|---|
| beryllium | 4 | 9.0 |
| magnesium | 12 | 24.3 |
| calcium | 20 | 40.1 |
| strontium | 38 | 87.6 |
Explain, in terms of their electronic configurations, why these elements are placed in Group 2 of the periodic table.
