Symbol
Cr
  
Ga
  
Period Number
4
  
4
  
Block
d block
  
p block
  
Element Family
Transition Metal
  
Post-Transition
  
Space Group Name
Im_ 3m
  
Cmca
  
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.
  
- A gram of Gallium metal can be bought for only three dollars.
- Gallium metal found in ores of following things Coal, Bauxite, Diaspore, Sphalerite, Germanite and Zinc.
  
Sources
Found in Minerals, Mining, Ores of metals, Ores of Minerals
  
Earth's crust, Found in Minerals, Mining, Ores of Minerals
  
History
  
  
Who Discovered
Louis Nicolas Vauquelin
  
Lecoq de Boisbaudran
  
Discovery
In Between 1797 - 1798
  
In 1875
  
Abundance
  
  
Abundance In Universe
1.5 * 10-3 %
  
7
Abundance In Sun
~0.000004 %
  
16
Abundance In Earth's Crust
Abundance In Humans
Not Available
  
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.
  
- Gallium arsenide is a very important component of many semiconductors and led manufacturing.
- Gallium nitride is also know as a semiconductor and it is used in Blu-ray technology, mobile smartphones and LED.
  
Industrial Uses
Automobile Industry, Chemical Industry
  
Electrical Industry, Electronic Industry
  
Medical Uses
NA
  
Surgical Instruments Manufacturing
  
Other Uses
Alloys
  
Alloys
  
Biological Properties
  
  
Toxicity
Highly Toxic
  
Non Toxic
  
Present in Human Body
Yes
  
Yes
  
In Blood
0.11 Blood/mg dm-3
  
12
0.08 Blood/mg dm-3
  
13
In Bone
0.33 p.p.m.
  
21
Not Available
  
Melting Point
1,857.00 °C
  
14
Boiling Point
2,672.00 °C
  
39
2,403.00 °C
  
99+
Appearance
  
  
Physical State
Solid
  
Solid
  
Color
Silver
  
Silvery White
  
Luster
Metallic
  
Metallic
  
Hardness
  
  
Vickers Hardness
1,060.00 MPa
  
10
Not Available
  
Speed of Sound
5,940.00 m/s
  
5
2,740.00 m/s
  
31
Optical Properties
  
  
Allotropes
No
  
No
  
α Allotropes
Not Available
  
Not Available
  
β Allotropes
Not Available
  
Not Available
  
γ Allotropes
Not Available
  
Not Available
  
Chemical Formula
Cr
  
Ga
  
Isotopes
  
  
Electronegativity
  
  
Pauling Electronegativity
Sanderson Electronegativity
Allred Rochow Electronegativity
Mulliken-Jaffe Electronegativity
Not Available
  
Electropositivity
  
  
Pauling Electropositivity
Ionization Energies
  
  
1st Energy Level
26,130.00 kJ/mol
  
1
578.80 kJ/mol
  
99+
2nd Energy Level
28,750.00 kJ/mol
  
1
1,979.30 kJ/mol
  
13
3rd Energy Level
34,230.00 kJ/mol
  
1
2,963.00 kJ/mol
  
28
4th Energy Level
37,066.00 kJ/mol
  
1
6,180.00 kJ/mol
  
8
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+
0.87 g/amp-hr
  
99+
Other Chemical Properties
Anti Corrosion, Chemical Stability, Ionization, Radioactive Isotopes, Solubility
  
Ionization, Radioactive Isotopes
  
Electron Configuration
[Ar] 3d5 4s1
  
[Ar] 3d10 4s2 4p1
  
Crystal Structure
Body Centered Cubic (BCC)
  
Orthorhombic (ORTH)
  
Crystal Lattice
BCC-Crystal-Structure-.jpg#100
  
ORTH-Crystal-Structure-of-Gallium.jpg#100
  
Atom
  
  
Radius of an Atom
  
  
Atomic Volume
7.23 cm3/mol
  
99+
11.80 cm3/mol
  
99+
Adjacent Atomic Numbers
  
  
Valence Electron Potential
170.00 (-eV)
  
4
69.70 (-eV)
  
19
Lattice Angles
π/2, π/2, π/2
  
π/2, π/2, π/2
  
Lattice C/A Ratio
Not Available
  
Not Available
  
Density
  
  
Density At Room Temperature
7.19 g/cm3
  
99+
5.91 g/cm3
  
99+
Density When Liquid (at m.p.)
6.10 g/cm3
  
99+
Tensile Strength
Not Available
  
Viscosity
Not Available
  
Not Available
  
Vapor Pressure
  
  
Vapor Pressure at 2000 K
Not Available
  
Elasticity properties
  
  
Shear Modulus
Not Available
  
Bulk Modulus
Not Available
  
Other Mechanical Properties
NA
  
NA
  
Magnetic Characteristics
  
  
Magnetic Ordering
Antiferromagnetic
  
Diamagnetic
  
Electrical Properties
  
  
Electrical Property
NA
  
Semiconductor
  
Resistivity
125.00 nΩ·m
  
27
270.00 nΩ·m
  
15
Electrical Conductivity
0.08 106/cm Ω
  
25
0.07 106/cm Ω
  
29
Electron Affinity
64.30 kJ/mol
  
15
28.90 kJ/mol
  
31
Specific Heat
0.45 J/(kg K)
  
12
0.37 J/(kg K)
  
16
Molar Heat Capacity
23.35 J/mol·K
  
99+
25.86 J/mol·K
  
35
Thermal Conductivity
93.90 W/m·K
  
17
40.60 W/m·K
  
34
Critical Temperature
Not Available
  
Not Available
  
Thermal Expansion
4.90 µm/(m·K)
  
99+
18.00 µm/(m·K)
  
24
Enthalpy
  
  
Enthalpy of Vaporization
348.80 kJ/mol
  
24
256.10 kJ/mol
  
36
Enthalpy of Fusion
15.31 kJ/mol
  
20
5.59 kJ/mol
  
99+
Enthalpy of Atomization
397.50 kJ/mol
  
21
276.10 kJ/mol
  
39
Standard Molar Entropy
23.80 J/mol.K
  
99+
40.80 J/mol.K
  
38