Cerium is a
metallic chemical element in group IIIb of periodic table; symbol Ce, soft,
lustrous, ductile, iron-color metal with hexagonal or cubic crystalline
structure; atomic number 58; atomic mass 140.12; melting point ca 799 C; boiling
point ca 3,426 C; specific gravity 6.77 g/cm3 at 25 C; oxidation
state +3 or +4; electronic config. [Xe]4f15d16s1. It is the most
abundant rare-earth element and the most reactive next to europium among the
lanthanide group. Lanthanide (or lanthanoid) series are the group of rare-earth elements from
lanthanum (atomic
numbers 57) to 71; their chemical properties are similar to each other. The chemical properties
of scandium and yttrium are also similar to the lanthanides;
these group are often referred to "rare earth elements".
Atomic
No.
|
Element
|
Symbol
|
CAS
RN
|
21 |
Scandium |
Sc
| 7440-20-2 |
39 |
Yttrium |
Y
| 7440-65-5 |
57 |
Lanthanum |
La | 7439-91-0 |
58 |
Cerium |
Ce | 7440-45-1 |
59 |
Praseodymium |
Pr | 7440-10-0 |
60 |
Neodymium |
Nd | 7440-00-8 |
61 |
Promethium |
Pm | 7440-12-2 |
62 |
Samarium |
Sm | 7440-19-9 |
63 |
Europium |
Eu | 7440-53-1 |
64 |
Gadolinium |
Gd | 7440-54-2 |
65 |
Terbium |
Tb | 7440-27-9 |
66 |
Dysprosium |
Dy | 7429-91-6 |
67 |
Holmium |
Ho | 7440-60-0 |
68 |
Erbium |
Er | 7440-52-0 |
69 |
Thulium |
Tm | 7440-30-4 |
70 |
Ytterbium |
Yb | 7440-64-4 |
71 |
7440-64-4 |
Lu | 7440-64-4 |
Cerium occurs chiefly in the minerals
monazite and bastnaesite. The naturally occurring element is made up of the
isotopes 136Ce 0.193%,
138Ce 0.250%,
140Ce 88.58%, and
142Ce 11.07% which is a
radioactive alpha emitter having a half-life of 5×1015 years. Cerium is
slightly harder than lead. It tarnishes rapidly in moist air but not in dry air.
It oxidizes slowly in cold water and rapidly in hot water. It reacts rapidly
with the solutions of alkalis and concentrated (or dilute) acids. Its oxidation
valence is readily transferred form 3 to 4 if compressed or cooled. Its shell
orbitals are relatively close between 4f and the outer. with Cerium of valence
+3 is referred to as cerous, while with valence 4 is as ceric. Generally cerous
salts are yellow to reddish while ceric slats are white. Minute particles of
pure cerium or some iron-cerium alloy ignite if scratched and are used as the
flint in cigarette and gas lighters. Cerium is used in making lamp mantles as
incandescence is formed when burned. Cerium is allied to form malleable iron,
harder stainless steel, heat resistant magnesium and aluminium alloys and
permanent magnets. It is also used as an opacifier and polisher in the glass
industry, in cored carbon arcs to increase the brilliance especially for the
motion picture industry, and as a liquid-liquid extraction agent to remove
fission products from spent uranium fuel. Cerium compounds
include;
- Ceric Oxide
CeO2 (CAS
RN:1306-38-3):
A pale-yellow to
white powder; soluble in sulfuric acid, insoluble in dilute acid and water; used in ceramics and as a polish for optical glass. Catalyst for hydrocarbon
cracking, styrene production and water-gas shift reaction. Thermal stabilizer
for alumina and in chemical regenerating process.
- Ceric
Sulfate Ce(SO4)2·xH2O
(CAS
RN:13590-82-4): Yellow needles
forming a basic salt with excess water; used in waterproofing, mildew-proofing,
and in dyeing and printing textiles.
- Ceric
Ammonium Nitrate (NH4)2Ce(NO3)6
(CAS
RN: 16774-21-3):
Oxidizer
- Ceric Ammonium Sulfate Ce(NH4)4(SO4)4
(CAS
RN: 10378-47-9,
Dihydrate): Oxidizer
- Ceric
Hydroxide Ce(OH)4
(CAS
RN: 12014-56-1)
- Cerous Acetate
Ce(OOCCH3)3·1.5H2O (CAS
RN: 537-00-8,
Sesquihydrate)
- Cerous
Bromide: CeBr3 (CAS
RN: 14457-87-5,
)
- Cerous
Carbonate Ce2(CO3)3
(CAS
RN: 537-01-9,
5838-16-7)
- Cerous
Chloride
CeCl3 (CAS
RN: 7790-86-5,
19423-76-8, 18618-55-8)
- Cerous
Fluoride CeF3:
White hexagonal
crystals, melting point 1460 C; used in arc carbons to increase the brilliance
of carbon-arc lamps.
- Cerous
Naphthenate: Used as drier/additive
for paints, coatings and inks; catalyst for
chemical reactions
- Cerous
Nitrate
Ce(NO3)3 (CAS
RN:10294-41-4,
Hydrate)
- Cerous
Oxalate:
Ce(C2O4)3·xH2O
(CAS
RN:139-42-4,
15750-47-7): Used in ceramics, glass, phosphors
and pyrotechnics
- Cerous
Perchlorate CeO9Cl3
(CAS
RN: 14017-47-1)
- Cerous Phosphate CeH2O5P
(CAS RN:13454-71-2)
- Cerous
Silicide
CeSi2
(CAS RN:12014-85-6)
- Cerium
Stearate Ce(C18H35O2)2 :White, waxy, inert
powder, melting point 100-110 C; used in waterproofing compounds and drier for
paint and ink.
- Cerous
Sulfide
Ce2S3
(CAS
RN:12014-93-6)
|