Chromium vs Rhodium
Periodic Table
Symbol
Cr
Rh
Group Number
6
12
9
9
Period Number
4
5
Block
d block
d block
Element Family
Transition Metal
Transition Metal
CAS Number
7440473
39
7440166
99+
Space Group Name
Im_ 3m
Fm_ 3m
Space Group Number
229.00
1
225.00
2
Facts
Interesting Facts
- Chromium is highly reactive, hence it is not found free in nature.
- Ores of Chromites mineral are the major source of Chromium metal.
- Almost 90% leather tanning is done with the help of chromium.
- Rhodium is the rarest element out of all non-radioactive metals on the earth .
- Rhodium is one of the most durable and hard metal, which also have high reflectance.
Sources
Found in Minerals, Mining, Ores of metals, Ores of Minerals
Earth's crust, Found As a By-product, Found in Minerals, Mining
History
Who Discovered
Louis Nicolas Vauquelin
William Hyde Wollaston
Discovery
In Between 1797 - 1798
In 1804
Abundance
Abundance In Universe
1.5 * 10-3 %
7
6 * 10-8 %
26
Abundance In Sun
~0.002 %
7
~0.0000002 %
25
Abundance In Meteorites
0.30 %
7
0.00 %
36
Abundance In Earth's Crust
0.01 %
13
0.00 %
99+
Abundance In Oceans
0.00 %
16
Not Available
Abundance In Humans
0.00 %
16
Not Available
Uses
Uses & Benefits
- It is used to harden the steel and produces a stainless steel and other various alloys.
- It is also used to give proper finish to polished mirrors. Its chromium plates are used in bathroom fittings.
- Rhodium metal is mainly used in catalytic converters for cars as it reduces nitrogen oxides in exhaust gases.
- It is used as an industrial catalyst for nitric acid, acetic acid, hydrogenation reaction, etc.
Industrial Uses
Automobile Industry, Chemical Industry
Aerospace Industry, Automobile Industry, Electrical Industry, Electronic Industry
Medical Uses
NA
NA
Other Uses
Alloys
Alloys
Biological Properties
Toxicity
Highly Toxic
NA
Present in Human Body
Yes
No
In Blood
0.11 Blood/mg dm-3
12
Not Available
In Bone
0.33 p.p.m.
21
Not Available
Physical Properties
Melting Point
1,857.00 °C
14
1,966.00 °C
12
Boiling Point
2,672.00 °C
39
3,727.00 °C
17
Appearance
Physical State
Solid
Solid
Color
Silver
Silvery White
Luster
Metallic
Metallic
Hardness
Mohs Hardness
8.50
1
6.00
6
Brinell Hardness
687.00 MPa
16
980.00 MPa
9
Vickers Hardness
1,060.00 MPa
10
1,100.00 MPa
9
Speed of Sound
5,940.00 m/s
5
4,700.00 m/s
15
Optical Properties
Reflectivity
Not Available
84.00 %
4
Allotropes
No
No
α Allotropes
Not Available
Not Available
β Allotropes
Not Available
Not Available
γ Allotropes
Not Available
Not Available
Chemical Properties
Chemical Formula
Cr
Rh
Isotopes
Known Isotopes
21
18
16
23
Electronegativity
Pauling Electronegativity
1.66
18
2.28
3
Sanderson Electronegativity
1.66
14
Not Available
Allred Rochow Electronegativity
1.56
10
1.45
16
Allen Electronegativity
1.65
19
1.56
24
Electropositivity
Pauling Electropositivity
2.34
36
1.72
99+
Ionization Energies
1st Energy Level
26,130.00 kJ/mol
1
719.70 kJ/mol
29
2nd Energy Level
28,750.00 kJ/mol
1
1,740.00 kJ/mol
26
3rd Energy Level
34,230.00 kJ/mol
1
2,997.00 kJ/mol
27
4th Energy Level
37,066.00 kJ/mol
1
Not Available
5th Energy Level
97,510.00 kJ/mol
1
Not Available
6th Energy Level
105,800.00 kJ/mol
1
Not Available
7th Energy level
114,300.00 kJ/mol
1
Not Available
8th Energy Level
125,300.00 kJ/mol
1
Not Available
9th Energy Level
134,700.00 kJ/mol
1
Not Available
10th Energy Level
144,300.00 kJ/mol
1
Not Available
11th Energy Level
26,130.00 kJ/mol
12
Not Available
12th Energy Level
28,750.00 kJ/mol
13
Not Available
13th Energy Level
34,230.00 kJ/mol
10
Not Available
14th Energy Level
37,066.00 kJ/mol
12
Not Available
15th Energy Level
97,510.00 kJ/mol
1
Not Available
16th Energy Level
105,800.00 kJ/mol
2
Not Available
17th Energy Level
114,300.00 kJ/mol
3
Not Available
18th Energy Level
125,300.00 kJ/mol
4
Not Available
19th Energy Level
134,700.00 kJ/mol
5
Not Available
20th Energy Level
144,300.00 kJ/mol
7
Not Available
21st Energy Level
157,700.00 kJ/mol
7
Not Available
22nd Energy Level
166,090.00 kJ/mol
6
Not Available
Electrochemical Equivalent
0.32 g/amp-hr
99+
1.28 g/amp-hr
99+
Electron Work Function
4.50 eV
14
4.98 eV
6
Other Chemical Properties
Anti Corrosion, Chemical Stability, Ionization, Radioactive Isotopes, Solubility
Anti Corrosion, Ionization, Radioactive Isotopes
Atomic Properties
Atomic Number
24
99+
45
99+
Electron Configuration
[Ar] 3d5 4s1
[Kr] 4d8 5s1
Crystal Structure
Body Centered Cubic (BCC)
Face Centered Cubic (FCC)
Crystal Lattice
BCC-Crystal-Structure-.jpg#100
FCC-Crystal-Structure-of-Rhodium.jpg#100
Atom
Number of Protons
24
99+
45
99+
Number of Neutrons
28
99+
58
99+
Number of Electrons
24
99+
45
99+
Radius of an Atom
Atomic Radius
128.00 pm
99+
134.00 pm
99+
Covalent Radius
139.00 pm
99+
142.00 pm
99+
Van der Waals Radius
200.00 pm
28
200.00 pm
28
Atomic Weight
52.00 amu
99+
102.91 amu
99+
Atomic Volume
7.23 cm3/mol
99+
8.30 cm3/mol
99+
Adjacent Atomic Numbers
Valence Electron Potential
170.00 (-eV)
4
64.00 (-eV)
22
Lattice Constant
291.00 pm
99+
380.34 pm
27
Lattice Angles
π/2, π/2, π/2
π/2, π/2, π/2
Lattice C/A Ratio
Not Available
Not Available
Mechanical Properties
Density
Density At Room Temperature
7.19 g/cm3
99+
12.41 g/cm3
28
Density When Liquid (at m.p.)
6.30 g/cm3
40
10.70 g/cm3
14
Tensile Strength
689.00 MPa
7
951.00 MPa
5
Viscosity
Not Available
Not Available
Vapor Pressure
Vapor Pressure at 1000 K
0.00 (Pa)
24
Not Available
Vapor Pressure at 2000 K
774.00 (Pa)
1
0.02 (Pa)
19
Elasticity properties
Shear Modulus
115.00 GPa
9
150.00 GPa
6
Bulk Modulus
160.00 GPa
11
275.00 GPa
5
Young's Modulus
279.00 GPa
8
380.00 GPa
5
Poisson Ratio
0.21
32
0.26
22
Other Mechanical Properties
NA
Malleable
Magnetic Properties
Magnetic Characteristics
Specific Gravity
7.19
99+
12.41
20
Magnetic Ordering
Antiferromagnetic
Paramagnetic
Electrical Properties
Electrical Property
NA
Conductor
Resistivity
125.00 nΩ·m
27
43.30 nΩ·m
99+
Electrical Conductivity
0.08 106/cm Ω
25
0.21 106/cm Ω
8
Electron Affinity
64.30 kJ/mol
15
109.70 kJ/mol
7
Thermal Properties
Specific Heat
0.45 J/(kg K)
12
0.24 J/(kg K)
22
Molar Heat Capacity
23.35 J/mol·K
99+
24.98 J/mol·K
99+
Thermal Conductivity
93.90 W/m·K
17
150.00 W/m·K
9
Critical Temperature
Not Available
Not Available
Thermal Expansion
4.90 µm/(m·K)
99+
8.20 µm/(m·K)
99+
Enthalpy
Enthalpy of Vaporization
348.80 kJ/mol
24
495.40 kJ/mol
12
Enthalpy of Fusion
15.31 kJ/mol
20
21.76 kJ/mol
10
Enthalpy of Atomization
397.50 kJ/mol
21
556.50 kJ/mol
12
Standard Molar Entropy
23.80 J/mol.K
99+
31.50 J/mol.K
99+
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