| Element | Symbol | At. No. | Electronic configuration | |
|---|---|---|---|---|
| Actinium | Ac | 89 | 6d–orbitals are filled up | [Rn] 6d17s2 |
| Rutherfordium | Rf | 104 | [Rn] 5f146d27s2 | |
| Hahnium | Ha | 105 | [Rn] 5f146d37s2 | |
| Seaborgium | Sg | 106 | [Rn] 5f146d47s2 | |
| Bohrium | Bh | 107 | [Rn] 5f146d57s2 | |
| Hassium | Hs | 108 | [Rn] 5f146d67s2 | |
| Meitnerium | Mt | 109 | [Rn] 5f146d77s2 | |
| Ununnilium | Uun | 110 | [Rn] 5f146d87s2 | |
| Unununium | Uuu | 111 | [Rn] 5f146d97s2 | |
| Unubium | Uub | 112 | [Rn] 5f146d107s2 | |
6d–series consists of elements Ac (atomic number 89) and those beyond Rutherfordium/Kurchatovium (atomic number 104). These elements lie in the seventh period. This period is still incomplete. At present this series consist of Ac89, Ku104, Ha105 and Unh106 (four elements). These elements involve the gradual filling of 6d orbitals. In between Ac89 and Ku104 there are 14 elements viz. Th90 to Lw103 which are called actinides or actinones. These 14 elements involve the progressive filling of 5f orbitals and hence do not belong to 6d–series. Thus at Lw103 5f orbitals are completely–filled. Consequently at Ac89, 5f orbitals are vacant (5f0 configuration) while in the remaining elements viz. Ku104, Ha105 and Unh106 (three elements), 5f orbitals are completely–filled (5f14 configuration).
Complete and valence–shell configurations of the atoms of 6d–series elements can be written as follows. Here [Rn]86=2, 8, 18, 32, 18, 8 (six shells).
Complete configuration = [Rn]86 5f06d1–47s2;
which is otherwise written as 2, 8, 18, 32, 5s2p6d10f
06s2p6d1–4, 7s2 (7shells)
valence–shell configuration =
5f0–14 6d1–47s2