Terbium
Table:
Terbium, 65Tb

Terbium
Pronunciation	/ˈtɜːrbiəm/ ⓘ ​(TUR-bee-əm)
Appearance	silvery white

Standard atomic weight Ar°(Tb)

158.925354±0.000007[1]
158.93±0.01 (abridged)[2]

Terbium in the periodic table

Hydrogen

Helium

Lithium

Beryllium

Boron

Carbon

Nitrogen

Oxygen

Fluorine

Neon

Sodium

Magnesium

Aluminium

Silicon

Phosphorus

Sulfur

Chlorine

Argon

Potassium

Calcium

Scandium

Titanium

Vanadium

Chromium

Manganese

Iron

Cobalt

Nickel

Copper

Zinc

Gallium

Germanium

Arsenic

Selenium

Bromine

Krypton

Rubidium

Strontium

Yttrium

Zirconium

Niobium

Molybdenum

Technetium

Ruthenium

Rhodium

Palladium

Silver

Cadmium

Indium

Tin

Antimony

Tellurium

Iodine

Xenon

Caesium

Barium

Lanthanum

Cerium

Praseodymium

Neodymium

Promethium

Samarium

Europium

Gadolinium

Terbium

Dysprosium

Holmium

Erbium

Thulium

Ytterbium

Lutetium

Hafnium

Tantalum

Tungsten

Rhenium

Osmium

Iridium

Platinum

Gold

Mercury (element)

Thallium

Lead

Bismuth

Polonium

Astatine

Radon

Francium

Radium

Actinium

Thorium

Protactinium

Uranium

Neptunium

Plutonium

Americium

Curium

Berkelium

Californium

Einsteinium

Fermium

Mendelevium

Nobelium

Lawrencium

Rutherfordium

Dubnium

Seaborgium

Bohrium

Hassium

Meitnerium

Darmstadtium

Roentgenium

Copernicium

Nihonium

Flerovium

Moscovium

Livermorium

Tennessine

Oganesson

–
↑
Tb
↓
Bk

gadolinium ← terbium → dysprosium

Atomic number (Z)	65
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f9 6s2
Electrons per shell	2, 8, 18, 27, 8, 2
Physical properties
Phase at STP	solid
Melting point	1629 K ​(1356 °C, ​2473 °F)
Boiling point	3396 K ​(3123 °C, ​5653 °F)
Density (at 20° C)	8.229 g/cm3 [3]
when liquid (at m.p.)	7.65 g/cm3
Heat of fusion	10.15 kJ/mol
Heat of vaporization	391 kJ/mol
Molar heat capacity	28.91 J/(mol·K)
Vapor pressure

P (Pa)

1

10

100

1 k

10 k

100 k

at T (K)

1789

1979

(2201)

(2505)

(2913)

(3491)

Atomic properties
Oxidation states	common: +3

0,[4] +1,[5] +2,[6] +4[7]
Electronegativity	Pauling scale: 1.2 (?)
Ionization energies

1st: 565.8 kJ/mol
2nd: 1110 kJ/mol
3rd: 2114 kJ/mol

Atomic radius	empirical: 177 pm
Covalent radius	194±5 pm

Spectral lines of terbium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp) (hP2)
Lattice constants

a = 360.56 pm
c = 569.66 pm (at 20 °C)[3]
Thermal expansion	at r.t. poly: 10.3 µm/(m⋅K)
Thermal conductivity	11.1 W/(m⋅K)
Electrical resistivity	α, poly: 1.150 µΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic at 300 K
Molar magnetic susceptibility	+146000×10−6 cm3/mol (273 K)[8]
Young's modulus	55.7 GPa
Shear modulus	22.1 GPa
Bulk modulus	38.7 GPa
Speed of sound thin rod	2620 m/s (at 20 °C)
Poisson ratio	0.261
Vickers hardness	450–865 MPa
Brinell hardness	675–1200 MPa
CAS Number	7440-27-9
History
Naming	after Ytterby (Sweden), where it was mined
Discovery and first isolation	Carl Gustaf Mosander (1843)
Isotopes of terbium

v
e

Main isotopes[9]

Decay

abun­dance

half-life (t1/2)

mode

pro­duct

157Tb

synth

71 y

ε

157Gd

158Tb

synth

180 y

ε

158Gd

β−

158Dy

159Tb

100%

stable

Category: Terbium

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Using the given table, state whether the hypothesis is entailed, neutral, or refuted. Give your final answer in JSON format {"answer": "YOUR ANSWER"}.

Claim: Terbium is a rare element.

answer: neutral