Terbium (Tb): electron configuration, atomic mass and facts
Terbium (Tb) is element 65 of the periodic table, a lanthanide in period 6 (f-block). Its electron configuration is [Xe] 4f9 6s2, with electrons arranged in shells 2, 8, 18, 27, 8, 2, and its standard atomic weight is 158.93 u.
▶ Watch Terbium’s electrons orbit in the interactive periodic tableTerbium at a glance
| Symbol | Tb |
|---|---|
| Atomic number | 65 |
| Atomic mass | 158.93 u |
| Category | Lanthanide |
| Group | f-block (no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f9 5s2 5p6 6s2 |
| Noble-gas shorthand | [Xe] 4f9 6s2 |
| Electrons per shell | 2, 8, 18, 27, 8, 2 |
| Electronegativity (Pauling) | 1.1 |
| State at 20 °C | solid |
Where is Terbium on the periodic table?
Terbium is in period 6 of the f-block, the lanthanide row printed below the main table. It has 6 electron shells, and this row is where the 4f subshell fills.
How to work out the electron configuration of Terbium
Put 65 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38), 4d¹⁰ (48), 5p⁶ (54), 6s² (56), 4f⁹ (65). In shorthand, [Xe] stands for the 54 electrons of xenon, giving [Xe] 4f⁹ 6s².
How electronegative is Terbium?
Terbium has a Pauling electronegativity of 1.1, ranking 87 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Frequently asked questions
What is the electron configuration of Terbium?
The electron configuration of Terbium (Tb) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f9 5s2 5p6 6s2. In noble-gas shorthand it is written [Xe] 4f9 6s2.
How many electrons does Terbium have in each shell?
Terbium has 65 electrons arranged in shells as 2, 8, 18, 27, 8, 2.
What is the atomic mass of Terbium?
The standard atomic weight of Terbium is 158.93 u, so one mole of Terbium atoms has a mass of about 158.93 g.
Is Terbium a metal?
Yes. Terbium is a lanthanide.
Explore nearby elements
More lanthanides: Samarium, Europium, Gadolinium, Dysprosium, Holmium, Erbium. See all elements on the periodic table.