Return
to the Main CHEMystery Page.
Return
to the Periodic Table of the Elements
Element 69 - Thulium (Tm)
From
Thule
, or Northland; discovered 1879. When irradiated in a nuclear reactor, thulium produces an isotope that gives off X-rays. A "button" of this isotope is used to make a lightweight, portable X-ray machine for medical use. The "hot" thulium is replaced every few months.
Properties
Atomic Number
:
69
Atomic Weight
:
168.9342
Electron Configuration
(at ground state):
1s
2
2s
2
2p
6
3s
2
3p
6
3d
10
4s
2
4p
6
4d
10
4f
13
5s
2
5p
6
6s
2
Oxidation States
(Bold most stable):
+3
, +2
Boiling Point
(K):
2223
Melting Point (K):
1818
Density
(at 300K -- g/cm
3
):
9.32
Atomic Volume (at 300K -- cm
3
/mol)
18.1
Number of stable
isotopes
:
1
Mass Number
(Bold naturally occurring) --
Half-Life
--
Disintigration Type
:
170 -- 128.6 days --
beta particle
(
electron
) emission
171 -- 1.92 years --
beta particle
(
electron
) emission
Covalent Radius (Å):
1.56
Atomic Radius (Å):
1.77
First
Ionization Potential
(V):
6.184
Electronegativity
(Pauling's):
1.25
Specific Heat
Capacity (at 300K -- J g
-1
K
-1
):
0.16
Heat of Vaporization (kJ/mol):
191
Heat of Fusion (kJ/mol):
16.8
Electrical Conductivity (at 293K for polycrystalline material -- 10
6
-1
cm
-1
):
1.3
Thermal Conductivity (at 300K -- W m
-1
K
-1
):
16.8
Crystal Structure:
Hexagonal
Acid
-
Base
Properties:
Slightly basic