İtterbiyûm (Yb)

element with the atomic number of 70

Atomic Number	70
Atomic Weight	173.045
Hejmara baristeyî	174

Group
Period	6
Block	f

Proton	70 p⁺
Notron	104 n⁰
Kareva	70 e^-

Physical Property

Atomic Radius	175 pm 277 pm
molar volume	24,8 cm³/mol
Covalent Radius	170 pm 129 pm 187 pm
Metallic Radius
ionic radius	102 pm 108 pm 114 pm 86,8 pm 92,5 pm 98,5 pm 104,2 pm
Crystal Radius	116 pm 122 pm 128 pm 100,8 pm 106,5 pm 112,5 pm 118,2 pm
Van der Waals radius	226 pm 279 pm 335,5 pm
density	6,9 g/cm³ 6.210 kg/m³

Chemical Property

{ERROR}

wize

proton affinity
electron affinity	-0,02 eV/particle
ionization energy	6,25416 eV/particle 12,179184 eV/particle 25,053 eV/particle 43,56 eV/particle 65,58 eV/particle 99 eV/particle 117 eV/particle 135 eV/particle 163 eV/particle 182 eV/particle 209 eV/particle 244 eV/particle 279 eV/particle 301 eV/particle 324 eV/particle 360 eV/particle 396 eV/particle 431 eV/particle 469 eV/particle 505 eV/particle 540 eV/particle 580 eV/particle 620 eV/particle 651 eV/particle 882 eV/particle 924 eV/particle 971 eV/particle 1.019 eV/particle 1.065 eV/particle 1.114 eV/particle 1.175 eV/particle 1.224 eV/particle 1.275 eV/particle 1.324 eV/particle 1.516 eV/particle 1.564 eV/particle 1.618 eV/particle 1.668 eV/particle 1.789 eV/particle 1.845 eV/particle 1.978 eV/particle 2.036,4 eV/particle 3.443 eV/particle 3.555 eV/particle 3.677 eV/particle 3.805 eV/particle 3.929 eV/particle 4.051 eV/particle 4.238 eV/particle 4.364 eV/particle 4.502 eV/particle 4.630 eV/particle 4.988 eV/particle 5.101 eV/particle 5.224 eV/particle 5.339 eV/particle 5.731 eV/particle 5.860 eV/particle 6.111 eV/particle 6.236 eV/particle 13.784 eV/particle 14.093 eV/particle 14.435 eV/particle 14.752 eV/particle 16.191 eV/particle 16.570 eV/particle 17.050 eV/particle 17.365,44 eV/particle 70.123,04 eV/particle 71.574,79 eV/particle

enthalpy of vaporization	159 kJ/mol
enthalpy of fusion	3,35 kJ/mol
standard enthalpy of formation	155,6 kJ/mol
Kareva

electron shell	2, 8, 18, 32, 8, 2

valence electron	2 ⓘ

electron configuration	[Xe] 4f¹⁴ 6s²ⓘ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 4f¹⁴ 6s²

oxidation number	0, 1, 2, 3
electronegativity	0.22119
Electrophilicity Index	0,7743018767771305 eV/particle
fundamental state of matter

phase of matter
gaseous state of matter
Boiling Point	1.469,15 K
Melting Point	1.097,15 K
critical pressure
critical temperature
triple point
appearance
color	Black #ff1493 #00bf38 #00bf38
appearance
refractive index
thermodynamic material property
Thermal Conductivity
thermal expansion	0,0000263 1/K
molar heat capacity	26,74 J/(mol K)
Specific Heat Capacity	0,155 J/(g⋅K)
heat capacity ratio
electrical properties
type	Conductor
electrical conductivity	3,6 MS/m
electrical resistivity	0,00000028 Ω*m
superconductivity
magnetism
type	paramagnetic
magnetic susceptibility (Mass)	0,0000000059 m³/Kg
magnetic susceptibility (Molar)	0,00000000102 m³/mol
magnetic susceptibility (Volume)	0,0000388
magnetic ordering
Germahiya Curie
Néel temperature
pêkhate
Crystal Structure	{ERROR}
lattice constant	5,49 Å
Lattice Angles	π/2, π/2, π/2
mechanical property
hardness	343 MPa 206 MPa
bulk modulus	31 GPa
shear modulus	9,9 GPa
Young's modulus	24 GPa
Poisson's ratio	0,21
Leza dengê	1.590 m/s
classification
Category	Actinides, Lanthanides
CAS Group
IUPAC Group
Glawe Number	18
Mendeleev Number	39
Pettifor Number	17
Geochemical Class	rare earth & related
Goldschmidt classification	litophile

other

Gas Basicity
polarizability	139 ± 6 a₀
C6 Dispersion Coefficient	1.910 a₀
allotrope
Neutron cross section	35
Neutron Mass Absorption	0,0076
quantum number	1S0
space group	225 (Fm_3m)

Isotopes of Ytterbium

Stable Isotopes	5
Unstable Isotopes	33
Natural Isotopes	7

¹⁴⁸Yb

Hejmara baristeyî	148
neutron number	78
Giraniya Atomê	147,967547 ± 0,000429 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)
β⁺ p (β⁺-delayed proton emission)

¹⁴⁹Yb

Hejmara baristeyî	149
neutron number	79
Giraniya Atomê	148,964219 ± 0,000322 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life	700 ± 200 ms
spin	1/2
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	2001
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	100%

¹⁵⁰Yb

Hejmara baristeyî	150
neutron number	80
Giraniya Atomê	149,958314 ± 0,000322 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	2000
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)

¹⁵¹Yb

Hejmara baristeyî	151
neutron number	81
Giraniya Atomê	150,955402453 ± 0,000322591 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life	1,6 ± 0,5 s
spin	1/2
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1985
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)

¹⁵²Yb

Hejmara baristeyî	152
neutron number	82
Giraniya Atomê	151,950326699 ± 0,000160718 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	3,03 ± 0,06 s
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1982
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁵³Yb

Hejmara baristeyî	153
neutron number	83
Giraniya Atomê	152,949372 ± 0,000215 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life	4,2 ± 0,2 s
spin	7/2
nuclear quadrupole moment
dema îcadkirinê yan keşfê	1977
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)
α (α emission)
β⁺ p (β⁺-delayed proton emission)	0.008%

¹⁵⁴Yb

Hejmara baristeyî	154
neutron number	84
Giraniya Atomê	153,946395696 ± 0,000018551 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	409 ± 2 ms
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1964
parity	+

decay mode	intensity
α (α emission)	92.6%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	7.4%

¹⁵⁵Yb

Hejmara baristeyî	155
neutron number	85
Giraniya Atomê	154,945783216 ± 0,00001782 Da
g-factor	-0,26 ± 0,0057142857142857
natural abundance
radioactivity	☢️ radioactive element
half-life	1,793 ± 0,02 s
spin	7/2
nuclear quadrupole moment	-0,5 ± 0,3
dema îcadkirinê yan keşfê	1964
parity	-

decay mode	intensity
α (α emission)	89%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	11%

¹⁵⁶Yb

Hejmara baristeyî	156
neutron number	86
Giraniya Atomê	155,942817096 ± 0,000009992 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	26,1 ± 0,7 s
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1970
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	90%
α (α emission)	10%

¹⁵⁷Yb

Hejmara baristeyî	157
neutron number	87
Giraniya Atomê	156,942651368 ± 0,000011706 Da
g-factor	-0,182 ± 0,0022857142857143
natural abundance
radioactivity	☢️ radioactive element
half-life	38,6 ± 1 s
spin	7/2
nuclear quadrupole moment
dema îcadkirinê yan keşfê	1970
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)

¹⁵⁸Yb

Hejmara baristeyî	158
neutron number	88
Giraniya Atomê	157,939871202 ± 0,000008559 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	1,49 ± 0,13 m
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1967
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	0.0021%

¹⁵⁹Yb

Hejmara baristeyî	159
neutron number	89
Giraniya Atomê	158,940060257 ± 0,000018874 Da
g-factor	-0,146 ± 0,0032
natural abundance
radioactivity	☢️ radioactive element
half-life	1,67 ± 0,09 m
spin	5/2
nuclear quadrupole moment	-0,22 ± 0,02
dema îcadkirinê yan keşfê	1975
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶⁰Yb

Hejmara baristeyî	160
neutron number	90
Giraniya Atomê	159,93755921 ± 0,0000059 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	4,8 ± 0,2 m
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1967
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶¹Yb

Hejmara baristeyî	161
neutron number	91
Giraniya Atomê	160,937912384 ± 0,000016211 Da
g-factor	-0,21733333333333 ± 0,0053333333333333
natural abundance
radioactivity	☢️ radioactive element
half-life	4,2 ± 0,2 m
spin	3/2
nuclear quadrupole moment	1,03 ± 0,02
dema îcadkirinê yan keşfê	1974
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶²Yb

Hejmara baristeyî	162
neutron number	92
Giraniya Atomê	161,935779342 ± 0,000016213 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	18,87 ± 0,19 m
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1963
parity	+

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶³Yb

Hejmara baristeyî	163
neutron number	93
Giraniya Atomê	162,936345406 ± 0,000016215 Da
g-factor	-0,24866666666667 ± 0,0053333333333333
natural abundance
radioactivity	☢️ radioactive element
half-life	11,05 ± 0,35 m
spin	3/2
nuclear quadrupole moment	1,24 ± 0,02
dema îcadkirinê yan keşfê	1967
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶⁴Yb

Hejmara baristeyî	164
neutron number	94
Giraniya Atomê	163,934500743 ± 0,000016217 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	75,8 ± 1,7 m
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1960
parity	+

decay mode	intensity
ϵ (electron capture)	100%

¹⁶⁵Yb

Hejmara baristeyî	165
neutron number	95
Giraniya Atomê	164,935270241 ± 0,00002849 Da
g-factor	0,1908 ± 0,0032
natural abundance
radioactivity	☢️ radioactive element
half-life	9,9 ± 0,3 m
spin	5/2
nuclear quadrupole moment	2,48 ± 0,04
dema îcadkirinê yan keşfê	1964
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶⁶Yb

Hejmara baristeyî	166
neutron number	96
Giraniya Atomê	165,933876439 ± 0,000007515 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	56,7 ± 0,1 h
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1954
parity	+

decay mode	intensity
ϵ (electron capture)	100%

¹⁶⁷Yb

Hejmara baristeyî	167
neutron number	97
Giraniya Atomê	166,934954069 ± 0,000004251 Da
g-factor	0,2484 ± 0,0032
natural abundance
radioactivity	☢️ radioactive element
half-life	17,5 ± 0,2 m
spin	5/2
nuclear quadrupole moment	2,7 ± 0,04
dema îcadkirinê yan keşfê	1954
parity	-

decay mode	intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁶⁸Yb

Hejmara baristeyî	168
neutron number	98
Giraniya Atomê	167,933891297 ± 0,0000001 Da
g-factor	0
natural abundance	0,123 ± 0,003
radioactivity	☢️ radioactive element
half-life
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1938
parity	+

decay mode	intensity
α (α emission)
2β⁺ (double β⁺ decay)

¹⁶⁹Yb

Hejmara baristeyî	169
neutron number	99
Giraniya Atomê	168,935184208 ± 0,000000191 Da
g-factor	-0,18085714285714 ± 0,0022857142857143
natural abundance
radioactivity	☢️ radioactive element
half-life	32,014 ± 0,005 d
spin	7/2
nuclear quadrupole moment	3,54 ± 0,06
dema îcadkirinê yan keşfê	1946
parity	+

decay mode	intensity
ϵ (electron capture)	100%

¹⁷⁰Yb

Hejmara baristeyî	170
neutron number	100
Giraniya Atomê	169,934767242 ± 0,000000011 Da
g-factor	0
natural abundance	2,982 ± 0,039
radioactivity	stable isotope
half-life	Not Radioactive ☢️
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1938
parity	+

¹⁷¹Yb

Hejmara baristeyî	171
neutron number	101
Giraniya Atomê	170,936331515 ± 0,000000013 Da
g-factor	0,9846 ± 0,0008
natural abundance	14,086 ± 0,14
radioactivity	stable isotope
half-life	Not Radioactive ☢️
spin	1/2
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1934
parity	-

¹⁷²Yb

Hejmara baristeyî	172
neutron number	102
Giraniya Atomê	171,936386654 ± 0,000000014 Da
g-factor	0
natural abundance	21,686 ± 0,13
radioactivity	stable isotope
half-life	Not Radioactive ☢️
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1934
parity	+

¹⁷³Yb

Hejmara baristeyî	173
neutron number	103
Giraniya Atomê	172,938216211 ± 0,000000012 Da
g-factor	-0,2712 ± 0,00024
natural abundance	16,103 ± 0,063
radioactivity	stable isotope
half-life	Not Radioactive ☢️
spin	5/2
nuclear quadrupole moment	2,8 ± 0,04
dema îcadkirinê yan keşfê	1934
parity	-

¹⁷⁴Yb

Hejmara baristeyî	174
neutron number	104
Giraniya Atomê	173,938867545 ± 0,000000011 Da
g-factor	0
natural abundance	32,025 ± 0,08
radioactivity	stable isotope
half-life	Not Radioactive ☢️
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1934
parity	+

¹⁷⁵Yb

Hejmara baristeyî	175
neutron number	105
Giraniya Atomê	174,941281907 ± 0,000000076 Da
g-factor	0,21885714285714 ± 0,0022857142857143
natural abundance
radioactivity	☢️ radioactive element
half-life	4,185 ± 0,001 d
spin	7/2
nuclear quadrupole moment	3,52 ± 0,05
dema îcadkirinê yan keşfê	1945
parity	-

decay mode	intensity
β⁻ (β⁻ decay)	100%

¹⁷⁶Yb

Hejmara baristeyî	176
neutron number	106
Giraniya Atomê	175,942574706 ± 0,000000015 Da
g-factor	0
natural abundance	12,995 ± 0,083
radioactivity	☢️ radioactive element
half-life
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1934
parity	+

decay mode	intensity
2β⁻ (double β⁻ decay)
α (α emission)

¹⁷⁷Yb

Hejmara baristeyî	177
neutron number	107
Giraniya Atomê	176,945263846 ± 0,000000236 Da
g-factor	-0,15444444444444 ± 0,0033333333333333
natural abundance
radioactivity	☢️ radioactive element
half-life	1,911 ± 0,003 h
spin	9/2
nuclear quadrupole moment	4,03 ± 0,06
dema îcadkirinê yan keşfê	1945
parity	+

decay mode	intensity
β⁻ (β⁻ decay)	100%

¹⁷⁸Yb

Hejmara baristeyî	178
neutron number	108
Giraniya Atomê	177,9466694 ± 0,000007072 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	74 ± 3 m
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1973
parity	+

decay mode	intensity
β⁻ (β⁻ decay)	100%

¹⁷⁹Yb

Hejmara baristeyî	179
neutron number	109
Giraniya Atomê	178,94993 ± 0,000215 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life	8 ± 0,4 m
spin	1/2
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1982
parity	-

decay mode	intensity
β⁻ (β⁻ decay)	100%

¹⁸⁰Yb

Hejmara baristeyî	180
neutron number	110
Giraniya Atomê	179,951991 ± 0,000322 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life	2,4 ± 0,5 m
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	1987
parity	+

decay mode	intensity
β⁻ (β⁻ decay)	100%

¹⁸¹Yb

Hejmara baristeyî	181
neutron number	111
Giraniya Atomê	180,95589 ± 0,00032 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	3/2
nuclear quadrupole moment
dema îcadkirinê yan keşfê	2000
parity	-

decay mode	intensity
β⁻ (β⁻ decay)

¹⁸²Yb

Hejmara baristeyî	182
neutron number	112
Giraniya Atomê	181,958239 ± 0,000429 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	2012
parity	+

decay mode	intensity
β⁻ (β⁻ decay)

¹⁸³Yb

Hejmara baristeyî	183
neutron number	113
Giraniya Atomê	182,962426 ± 0,000429 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	3/2
nuclear quadrupole moment
dema îcadkirinê yan keşfê	2012
parity	-

decay mode	intensity
β⁻ (β⁻ decay)

¹⁸⁴Yb

Hejmara baristeyî	184
neutron number	114
Giraniya Atomê	183,965002 ± 0,00054 Da
g-factor	0
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	0
nuclear quadrupole moment	0
dema îcadkirinê yan keşfê	2012
parity	+

decay mode	intensity
β⁻ (β⁻ decay)

¹⁸⁵Yb

Hejmara baristeyî	185
neutron number	115
Giraniya Atomê	184,969425 ± 0,000537 Da
g-factor
natural abundance
radioactivity	☢️ radioactive element
half-life
spin	9/2
nuclear quadrupole moment
dema îcadkirinê yan keşfê	2012
parity	-

decay mode	intensity
β⁻ (β⁻ decay)

dîrok

kaşîf an îcadker	Jean de Marignac
location of discovery	Switzerland
dema îcadkirinê yan keşfê	1878
Bêjenasî	Named for the Swedish village of Ytterby.
pronunciation	i-TUR-bi-em (îngilîzî)

source

Abundance
Abundance in Earth's crust	3,2 mg/kg
natural abundance (Okyanûs)	0,00000082 mg/L
natural abundance (human body)
natural abundance (meteoroid)	0,000018 %
natural abundance (Roj)	0,0000001 %
Abundance in Universe	0,0000002 %

Nuclear Screening Constants

1	s	1.3611
2	p	4.3716
2	s	18.306
3	d	13.6033
3	p	20.6635
3	s	21.2398
4	d	36.4104
4	f	40.568
4	p	33.598
4	s	32.4824
5	p	52.1685
5	s	49.85
6	s	61.4068

İtterbiyûm on ChemicalAid

ytterbium

İtterbiyûm (Yb)

Physical Property

Chemical Property

other

Isotopes of Ytterbium

148Yb

149Yb

150Yb

151Yb

152Yb

153Yb

154Yb

155Yb

156Yb

157Yb

158Yb

159Yb

160Yb

161Yb

162Yb

163Yb

164Yb

165Yb

166Yb

167Yb

168Yb

169Yb

170Yb

171Yb

172Yb

173Yb

174Yb

175Yb

176Yb

177Yb

178Yb

179Yb

180Yb

181Yb

182Yb

183Yb

184Yb

185Yb

dîrok

source

Nuclear Screening Constants

¹⁴⁸Yb

¹⁴⁹Yb

¹⁵⁰Yb

¹⁵¹Yb

¹⁵²Yb

¹⁵³Yb

¹⁵⁴Yb

¹⁵⁵Yb

¹⁵⁶Yb

¹⁵⁷Yb

¹⁵⁸Yb

¹⁵⁹Yb

¹⁶⁰Yb

¹⁶¹Yb

¹⁶²Yb

¹⁶³Yb

¹⁶⁴Yb

¹⁶⁵Yb

¹⁶⁶Yb

¹⁶⁷Yb

¹⁶⁸Yb

¹⁶⁹Yb

¹⁷⁰Yb

¹⁷¹Yb

¹⁷²Yb

¹⁷³Yb

¹⁷⁴Yb

¹⁷⁵Yb

¹⁷⁶Yb

¹⁷⁷Yb

¹⁷⁸Yb

¹⁷⁹Yb

¹⁸⁰Yb

¹⁸¹Yb

¹⁸²Yb

¹⁸³Yb

¹⁸⁴Yb

¹⁸⁵Yb