Terbium
LANTHANOID · GROUP None · PERIOD 6
65
Tb
Terbium
158.93
Atomic Data
| Atomic Number | 65 |
| Symbol | Tb |
| Atomic Weight | 158.93 u |
| Density (STP) | 8.23 g/cm³ |
| Melting Point | 1355.85 °C (1629 K) |
| Boiling Point | 3229.85 °C (3503 K) |
| Electronegativity | 1.2 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f9 5s2 5p6 6s2 |
| Oxidation States | +3, +4 |
| Phase at STP | Solid |
| Category | Lanthanoid |
| Period / Group | 6 / None |
| CAS Number | 7440-27-9 |
Electron Configuration
{{BOHR_SVG}}
[Xe] 4f9 6s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| N | 4 | 4f | 9 | 55 |
| O | 5 | 5s | 2 | 57 |
| O | 5 | 5p | 6 | 63 |
| P | 6 | 6s | 2 | 65 |
| Total | 65 | 65 | ||
Isotopes of Terbium
Terbium is monoisotopic — ¹⁵⁹Tb is its only naturally occurring stable isotope, accounting for 100% of all natural Terbium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Terbium-159 | ¹⁵⁹Tb | 65 | 94 | 100 | Stable |
Abundance & Occurrence
Terbium is present in Earth's crust at approximately 1.2 ppm by mass and at approximately 0.05 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Terbium
1.2 ppm
Silicon (ref.)
277,000 ppm
Oxygen (ref.)
461,000 ppm
Universe (ppm by mass)
Terbium
0.05 ppm
Helium (ref.)
230,000 ppm
Hydrogen (ref.)
739,000 ppm
Discovery & History
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Safety & Handling
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Terbium in the Real World
Real-World Uses
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Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.