Simply following electron configurations, hydrogen (electronic configuration 1s1) and helium (1s2) should be placed in groups 1 and 2, above lithium (1s22s1) and beryllium (1s22s2).
Hvis man blot fulgte elektronkonfigurationerne skulle hydrogen (elektronkonfiguration 1s1) og helium (1s2) placeres i gruppe 1 og 2, over lithium (2s1) og beryllium (2s2).