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The Element Iron
Iron Facts
Chemical & Physical
Properties of Iron
by Anne Marie Helmenstine, Ph.D.
Iron Basic Facts:
Symbol: Fe
Atomic
Number: 26
Atomic Weight: 55.847
Element Classification: Transition Metal
Atomic Weight: 55.847
Element Classification: Transition Metal
CAS Number 7439-89-6
Iron Periodic Table Location
Group: 8
Period:4
Block: d
Period:4
Block: d
Iron Electron Configuration
Short Form: [Ar]3d64s2
Long Form: 1s22s22p63s23p63d64s2
Shell Structure: 2 8 14 2
Long Form: 1s22s22p63s23p63d64s2
Shell Structure: 2 8 14 2
Iron Discovery
Discovery Date: Ancient Times
Name: Iron
derives its name from the Anglo-Saxon 'iren'. The element
symbol, Fe, was shortened from the Latin word 'ferrum' meaning 'firmness'.
History: Ancient
Egyptian iron objects have been dated to around 3500 B.C. These objects also
contain approximately 8% nickel showing the iron may have originally been part
of a meteorite.
The "Iron Age"
began around 1500 B.C. when the Hittites of Asia Minor began to smelt iron ore
and make iron tools.
Iron Physical Data
State at room temperature (300 K):
Solid
Appearance: malleable,
ductile, silvery metal
Density: 7.870 g/cc (25 °C)
Density at Melting Point: 6.98 g/cc
Specific Gravity: 7.874 (20 °C)
Melting Point: 1811 K
Boiling Point: 3133.35 K
Critical Point: 9250 K at 8750 bar
Heat of Fusion 14.9 kJ/mol
Heat of Vaporization: 351 kJ/mol
Molar Heat Capacity: 25.1 J/mol·K
Specific Heat: 0.443 J/g·K (at 20 °C)
Density: 7.870 g/cc (25 °C)
Density at Melting Point: 6.98 g/cc
Specific Gravity: 7.874 (20 °C)
Melting Point: 1811 K
Boiling Point: 3133.35 K
Critical Point: 9250 K at 8750 bar
Heat of Fusion 14.9 kJ/mol
Heat of Vaporization: 351 kJ/mol
Molar Heat Capacity: 25.1 J/mol·K
Specific Heat: 0.443 J/g·K (at 20 °C)
Iron Atomic Data
Oxidation States (Bold most common): +6,
+5, +4, +3, +2, +1, 0, -1, and -2
Electronegativity: 1.96 (for oxidation state +3) and 1.83 (for oxidation state +2)
Electron Affinity: 14.564 kJ/mol
Atomic Radius: 1.26 Å
Atomic Volume: 7.1 cc/mol
Ionic Radius: 64 (+3e) and 74 (+2e)
Covalent Radius: 1.24 Å
First Ionization Energy: 762.465 kJ/mol
Second Ionization Energy: 1561.874 kJ/mol
Third Ionization Energy: 2957.466 kJ/mol
Electronegativity: 1.96 (for oxidation state +3) and 1.83 (for oxidation state +2)
Electron Affinity: 14.564 kJ/mol
Atomic Radius: 1.26 Å
Atomic Volume: 7.1 cc/mol
Ionic Radius: 64 (+3e) and 74 (+2e)
Covalent Radius: 1.24 Å
First Ionization Energy: 762.465 kJ/mol
Second Ionization Energy: 1561.874 kJ/mol
Third Ionization Energy: 2957.466 kJ/mol
Iron Nuclear Data
Number of isotopes: 14 isotopes are known.
Naturally occuring iron is made up of four isotopes.
Natural Isotopes and % abundance: 54Fe (5.845),56Fe (91.754), 57Fe (2.119) and 58Fe (0.282)Iron Crystal Data
Natural Isotopes and % abundance: 54Fe (5.845),56Fe (91.754), 57Fe (2.119) and 58Fe (0.282)Iron Crystal Data
Lattice Structure: Body-Centered
Cubic
Lattice Constant: 2.870 Å
Debye Temperature: 460.00 K
Lattice Constant: 2.870 Å
Debye Temperature: 460.00 K
Iron Uses
Iron
is vital to plant and animal life. Iron is the active part of the hemoglobin
molecule our bodies use to transport oxygen from the lungs to the rest of the
body.
Iron metal is widely alloyed
with other metals and carbon for a multiple commercial uses.
Pig iron is an alloy
containing about 3-5% carbon, with varying quantities of Si, S, P, and Mn. Pig
iron is brittle, hard, and fairly fusible and is used to produce other iron
alloys, including steel.
Wrought iron contains only a
few tenths of a percent of carbon and is malleable, tough, and less fusible
than pig iron. Wrought iron typically has a fibrous structure.
Carbon steel is an iron alloy
with carbon and small amounts of S, Si, Mn, and P.
Alloy steels are carbon
steels that contain additives such as chromium, nickel, vanadium, etc.
Iron is the least expensive,
most abundant, and most used of all metals.
Miscellaneous Iron Facts
· Iron is the 4th most abundant element in the Earth's crust.
The Earth's core is believed to be comprised primarily of iron.
· Pure iron is chemically reactive and corrodes rapidly,
especially in moist air or at elevated temperatures.
· There are four allotropes of iron known as 'ferrites'. These are
designated α-, β-, γ-, and δ- with transition points at 770, 928, and 1530 °C.
The α- and β- ferrites have the same crystal structure, but when the α- form
becomes the β- form, the magnetism disappears.
· The most common iron ore is hematite (Fe2O3 mostly).
Iron is also found in magnetite (Fe3O4) and
taconite (a sedimentary rock containing more than 15% iron mixed with quartz).
· The top three countries that mine iron are Ukraine, Russia and
China. China, Australia and Brazil lead the world in iron production.
· Many meteorites have been found to contain high levels of iron.
· Iron is found in the sun and other stars.
· Iron is an essential mineral for health, but too much iron is
extremely toxic. Free iron in the blood reacts with peroxides to form
free radicals that damage DNA, protein, lipids and other cellular components,
leading to illness and sometimes death. 20 milligrams of iron per kilogram of
body weight is toxic, while 60 milligrams per kilogram is lethal.
· Iron is essential for the development of brain development.
Children with iron deficiencies show a lower ability to learn.
· Iron burns with a gold color in a flame test.
· Iron is used in fireworks to make sparks. The color of the
sparks will depend on the temperature of the iron.
Anne Marie Helmenstine,
Ph.D.
· Ph.D. in biomedical sciences from the University of
Tennessee at Knoxville - Oak Ridge National Laboratory.
· Science educator with experience teaching
chemistry, biology, astronomy, and physics at the high school, college, and
graduate levels.
· ThoughtCo and About Education chemistry expert
since 2001.
· Widely-published graphic artist, responsible for
printable periodic tables and other illustrations used in science.
Experience
Anne Helmenstine, Ph.D. has covered
chemistry for ThoughtCo and About Education since 2001, and other sciences
since 2013. She taught chemistry, biology, astronomy, and physics at the high
school, college, and graduate levels. She has worked as a research
scientist and also abstracting and indexing diverse scientific literature for
the Department of Energy.
In addition to her work as a science writer, Dr.
Helmenstine currently serves as a scientific consultant, specializing in
problems requiring an interdisciplinary approach. Previously, she worked
as a research scientist and college professor.
Education
Dr. Helmenstine holds a Ph.D. in biomedical
sciences from the University of Tennessee at Knoxville and a B.A.
in physics and mathematics with a minor in chemistry from Hastings
College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive
chemical detection and medical diagnostic tests.
Anne Marie Helmenstine, Ph.D.
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