La - Lanthanum

The placement of lanthanum in the d block instead of the f block of the table is controversial, and we may change, pending a review of the data. The element was discovered by Mosander in 1839 in Sweden.

Atomic number - 57 Density g/mL 6 .7

Atomic weight u 138 .9055 Melting point K 1193

Bonding radius A 1 .69 Boiling point K 3730

Atomic radius A 2 .74 Heat of vaporization kJ/mol 414

Ionization Potential V 5 .58 Heat of fusion kJ/mol 6 .2

Electronegativity - 1 .1 Specific heat J/gK 0 .19

The oxide is a strong base.
Crystal are hexagonal.

Electron config. : [Xe] 5d¹ 6s²

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac** Rf Db Sg Bh Hs Mt 110 111 112 113

Lanthanides* Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Actinides ** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Isotopes of La: Click mass number for decay process, product for element page.

120
2.8 sec
EC/ECp,11.200
Ba-120/Cs-119
119.93805 121
5.3 sec
EC,7.900 MeV
Ba-121
120.93301 122
8.7 sec
EC/ECp,9.700
Ba-122/Cs-121
121.93075 123
17 sec
EC,6.900 MeV
Ba-123
122.92624 124
29 sec
EC,8.800 MeV
Ba-124
123.92452 125
76 sec
EC,5.600 MeV
Ba-125
124.92066 126
54 sec
EC,7.600 MeV
Ba-126
125.91937

127
5.1 min
EC,4.690 MeV
Ba-127
126.91615 128
5.0 min
EC,6.700 MeV
Ba-128
127.91540 129
11.6 min
EC,3.720 MeV
Ba-129
128.91266 130
8.7 min
EC,5.600 MeV
Ba-130
129.91232 131
59 min
EC,2.960 MeV
Ba-131
130.91011 132
4.8 hr
EC,4.710 MeV
Ba-132
131.91011 133
3.912 hr
EC,2.230 MeV
Ba-133
132.90839

134
6.45 min
EC,3.710 MeV
Ba-134
133.90849 135
19.5 hr
EC,1.200 MeV
Ba-135
134.90697 136
9.87 min
EC,2.870 MeV
Ba-136
135.90765 137
6E+4 yr
EC,1.176 MeV
Ba-137
136.90646 138 0.0902%
1.05E+11 yr
B-/EC,1.737
Ce-138/Ba-138
137.90710 139 99.9098%

Stable

138.90634 140
1.6781 da
B-,3.762 MeV
Ce-140
139.90947

141
3.92 hr
B-,2.502 MeV
Ce-141
140.91095 142
91.1 min
B-,4.505 MeV
Ce-142
141.91407 143
14.2 min
B-,3.425 MeV
Ce-143
142.91605 144
40.8 sec
B-,5.540 MeV
Ce-144
143.91959 145
24.8 sec
B-,4.120 MeV
Ce-145
144.92165 146
6.27 sec
B-,6.550 MeV
Ce-146
145.92575 147
4.015 sec
B-/B-n,4.950
Ce-147/Ce-146
146.92781

148
1.428 sec
B-/B-n,7.260
Ce-148/Ce-147
147.93219 149
1.05 sec
B-/B-n,5.500
Ce-149/Ce-148
148.93419 150
0.86 sec
B-/B-n,7.800
Ce-150/Ce-149
149.93859 152
150 nsec
B-,9.100 MeV
Ce-152
151.94610 MASS abund.
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass

Updated by clh on 2/6/98. This is not a publication of Phoenix College.

Atomic number	-	57		Density	g/mL	6	.7
Atomic weight	u	138	.9055	Melting point	K	1193
Bonding radius	A	1	.69	Boiling point	K	3730
Atomic radius	A	2	.74	Heat of vaporization	kJ/mol	414
Ionization Potential	V	5	.58	Heat of fusion	kJ/mol	6	.2
Electronegativity	-	1	.1	Specific heat	J/gK	0	.19
The oxide is a strong base.				Crystal are hexagonal.
Electron config. : [Xe] 5d¹ 6s²
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120 2.8 sec EC/ECp,11.200 Ba-120/Cs-119 119.93805	121 5.3 sec EC,7.900 MeV Ba-121 120.93301	122 8.7 sec EC/ECp,9.700 Ba-122/Cs-121 121.93075	123 17 sec EC,6.900 MeV Ba-123 122.92624	124 29 sec EC,8.800 MeV Ba-124 123.92452	125 76 sec EC,5.600 MeV Ba-125 124.92066	126 54 sec EC,7.600 MeV Ba-126 125.91937
127 5.1 min EC,4.690 MeV Ba-127 126.91615	128 5.0 min EC,6.700 MeV Ba-128 127.91540	129 11.6 min EC,3.720 MeV Ba-129 128.91266	130 8.7 min EC,5.600 MeV Ba-130 129.91232	131 59 min EC,2.960 MeV Ba-131 130.91011	132 4.8 hr EC,4.710 MeV Ba-132 131.91011	133 3.912 hr EC,2.230 MeV Ba-133 132.90839
134 6.45 min EC,3.710 MeV Ba-134 133.90849	135 19.5 hr EC,1.200 MeV Ba-135 134.90697	136 9.87 min EC,2.870 MeV Ba-136 135.90765	137 6E+4 yr EC,1.176 MeV Ba-137 136.90646	138 0.0902% 1.05E+11 yr B-/EC,1.737 Ce-138/Ba-138 137.90710	139 99.9098% Stable 138.90634	140 1.6781 da B-,3.762 MeV Ce-140 139.90947
141 3.92 hr B-,2.502 MeV Ce-141 140.91095	142 91.1 min B-,4.505 MeV Ce-142 141.91407	143 14.2 min B-,3.425 MeV Ce-143 142.91605	144 40.8 sec B-,5.540 MeV Ce-144 143.91959	145 24.8 sec B-,4.120 MeV Ce-145 144.92165	146 6.27 sec B-,6.550 MeV Ce-146 145.92575	147 4.015 sec B-/B-n,4.950 Ce-147/Ce-146 146.92781
148 1.428 sec B-/B-n,7.260 Ce-148/Ce-147 147.93219	149 1.05 sec B-/B-n,5.500 Ce-149/Ce-148 148.93419	150 0.86 sec B-/B-n,7.800 Ce-150/Ce-149 149.93859	152 150 nsec B-,9.100 MeV Ce-152 151.94610	MASS abund. Halflife Particle, Energy Decay Product(s) Isotopic Mass