Periodic Table and Electrons Arrangement
- The classification of Group and Period are totally related to the electron arrangement of the atoms. As shown in the table above, the classification of elements in a periodic table is as follows:
- All the elements in the same group have an equal number of valence electron(s) (outer most electron)
- All the elements in the same period have an equal number of electron shell(s) (orbit).
- For example, the electron arrangement of calcium is 2.8.8.2. It has 2 valence electron and 4 electron shell. Therefore, it is placed in Group 2, period 4.
- Hydrogen, the simplest element atom, with 1 electron, does not fit into any group. (Even though some of the periodic tables place it in Group 1, due to its 1 (and the only one electron) valence electron.
| Number of Valence Electron in a Group | |
| Group | Number of Valence Electron |
| Group 1 | 1 |
| Group 2 | 2 |
| Group 13 | 3 |
| Group 14 | 4 |
| Group 15 | 5 |
| Group 16 | 6 |
| Group 17 | 7 |
| Group 18 | 8 |
