What is Iron: Definition and 517 Discussions

Iron () is a chemical element with symbol Fe (from Latin: ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in front of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust.
In its metallic state, iron is rare in the Earth's crust, limited mainly to deposition by meteorites. Iron ores, by contrast, are among the most abundant in the Earth's crust, although extracting usable metal from them requires kilns or furnaces capable of reaching 1,500 °C (2,730 °F) or higher, about 500 °C (900 °F) higher than that required to smelt copper. Humans started to master that process in Eurasia by about 2000 BCE, and the use of iron tools and weapons began to displace copper alloys, in some regions, only around 1200 BCE. That event is considered the transition from the Bronze Age to the Iron Age. In the modern world, iron alloys, such as steel, stainless steel, cast iron and special steels are by far the most common industrial metals, because of their mechanical properties and low cost.
Pristine and smooth pure iron surfaces are mirror-like silvery-gray. However, iron reacts readily with oxygen and water to give brown to black hydrated iron oxides, commonly known as rust. Unlike the oxides of some other metals, that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion. Although iron readily reacts, high purity iron, called electrolytic iron, has better corrosion resistance.
The body of an adult human contains about 4 grams (0.005% body weight) of iron, mostly in hemoglobin and myoglobin. These two proteins play essential roles in vertebrate metabolism, respectively oxygen transport by blood and oxygen storage in muscles. To maintain the necessary levels, human iron metabolism requires a minimum of iron in the diet. Iron is also the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals.Chemically, the most common oxidation states of iron are iron(II) and iron(III). Iron shares many properties of other transition metals, including the other group 8 elements, ruthenium and osmium. Iron forms compounds in a wide range of oxidation states, −2 to +7. Iron also forms many coordination compounds; some of them, such as ferrocene, ferrioxalate, and Prussian blue, have substantial industrial, medical, or research applications.

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  1. sbrothy

    Working with metal? - The "Forged in Iron" series

    I've never been a fan of working with iron or steel. Unforgiving material. I had no time for that. But recently, having seen the TV-show "Forged in Fire" on the History channel here in Denmark , I sorta realized I may have missed something. I hate quizzes, reality shows and the like but this one...
  2. L

    Chemistry FeCO3 oxidation formulation help

    Hi there, I did an exercise and when we corrected it I realised that the oxidation number of Fe was (ll) but I don't know how can I find it. The common name is iron (ll) nitrate and the other name, that I don't know how is called because i study this in basque, is iron (2+) nitrate trioxide (2-)
  3. A

    Electrolysis: Dark blue oxide from steel?

    Hi there, I have been trying to make iron oxide through electrolysis, I am using salt water as the electrolyte and an old alloyed steel (I am assuming iron and carbon) square pipe as the anode and a Rebar cathode. Unfortunately the beaker gets filled with this dark bluey color and when...
  4. O

    How to calculate iron losses in a steel ring around a conductor?

    Hi I'm looking for calculation example how to calculate iron losses in steel ring around current carrying conductor. I have tried to find examples online, but without a suitable result.
  5. H

    History Where did ancient civilizations get their supply of iron?

    Back in the 19th century British explorers came across Eskimos who were so isolated that they'd forgotten that any other humans existed. Nevertheless they had a little bit of iron that they used to put an edge on their knives. They had no trade so where did they get it? Fortunately their...
  6. rogdal

    Classical magnetic dipole-dipole interaction in iron

    I'm having a bit of trouble with this exercise because, even if I understand the physics of the dipole-dipole interaction in an ideal classical system, I don't get to know how to approach this problem. I've got a few doubts about how this system would work. First of all, what would be the...
  7. B

    Iron Maiden's "To Tame a Land" question

    I heard somewhere that Iron Maiden originally wanted to name their song "To Tame a Land" Dune but Frank Herbert did not give his permission as he was not a fan of their type of music. Has anyone else heard this before? Is this documented anywhere? Thanks in advance, clb
  8. C

    Is it possible to build a low-voltage Thompson jumping ring apparatus?

    Hi all, I'm attempting to build a jumping ring apparatus (a core of iron with the bottom wrapped with wiring like an electromagnet, so that when a metal ring is placed on top of the coil and a current is run through the coil, the ring jumps up into the air). Looking on the internet, I'm seeing a...
  9. M

    I Coil Around A Tube - Iron Cylinder Inside Tube - How Many Turns Needed?

    Hello, I am wanting to wrap a coil of wire around a tube, suspend an iron cylinder in the tube, energize the coil, and have it be able to suspend around 500 pounds on the iron cylinder. I was playing around with some online calculators for coils, and didn't really get anywhere, so I figured I...
  10. Kisen

    How much electrical energy can be extracted from Iron in a cell?

    Hi, I am trying to get to an answer for the following scenario. Imagine you have an electrochemical cell in its most basic terms. On the negative electrode you have 3 moles of iron metal in a chloride solution. On the positive side you have 3 moles FeCl3 solution. These are separated by a...
  11. StellarisVoid

    I need a functioning Soldering Iron....

    Hello, I have made a few circuits before, and I attempted to transfer it onto stripboards. I am not sure what the problem is, but it went terrible. I was using a Holife Soldering Iron (I don't know the model) and some lead-free solder I got from Bitsbox that is supposed to melt really well at...
  12. P

    I What are the possible states of cold iron balls?

    This thread is meant to discuss a topic that arose in https://www.physicsforums.com/threads/is-there-a-theoretical-size-limit-of-a-planet.1045983/ in a more precisely specified, idealized way. Further details: 1) Standard model + GR assumed, no other theories intended for this...
  13. L

    B Calculating Force on an Iron Object with Magnetic Field

    I have a scenario where I would like to calculate the electronics needed to create a force (pull on) an iron object. The set up is a coil (solenoid) with a steel (iron) object. I use Maxwell's equation (Ampere's law) to estimate the magnetic field B of the solenoid. My question is, how to...
  14. EmeraldPlatypus

    I Force exerted by an iron core electromagnet on a ferrofluid

    I am trying more generally to find the equation of the fore exerted by an electromagnet. The one that I keep finding is F=((NI)^2 A mu0)/2X^2. N is turn number, I is current, Mu0 is permeability of free space, A is the area of the core and X is the distance from the electromagnet. I take...
  15. nomadreid

    Heme iron and cardiovascular disease

    In the "Results" section of the Abstract of https://pubmed.ncbi.nlm.nih.gov/23708150/, (due to a paywall, I get no further) there is the following "The dose-response RR of CHD for an increase in heme iron intake of 1 mg/day was 1.27" (CHD being coronary heart disease). Is the paraphrasing in...
  16. A

    Fixing a Broken Soldering Iron: Repairing vs. Battery-Powered Options

    1 Is it possible to repair a Soldering iron which is not working? 2 Can we design and construct a Soldering iron working on Batteries instead of AC mains supply?
  17. L

    An iron cylinder inside a solenoid

    From ##\oint_{\Gamma}\vec{H}\cdot d\vec{l}=\sum I## by Ampere's Law which gives ##H \Delta l=\Delta N\cdot i\Leftrightarrow H=n i## where ##n=## number of turns per unit length so ##i=\frac{H}{n}=\frac{10^3 A / m}{\frac{200}{0.2m}}=1 A##. Since ##\vec{H}=\frac{\vec{B}-\mu_0\vec{M}}{\mu_0}## we...
  18. W

    Thermal Physics Problem -- Dropping a hot mass of iron into 20C water

    Hi, The solution for this question is thermal energy lost= thermal energy gained 0.200x450x(300-T)=1.0x4200x(T-20) T=26 degrees celcius. However, I am struggling to grasp why (300-T) is used. I have always known a change in something to be final - initial. Therefore change in T= Final-...
  19. S

    B Iron, Nuclear Stability and Nuclear Energy

    Iron (Fe-56) is in terms of nuclear energy spent, which seems equivalent to saying its nuclides are the most tightly-bound. Does this also make Fe-56 the most stable nucleus, and is nuclear potential energy to stability a general correlation? Do more-stable nuclei generally have less nuclear...
  20. xWaldorf

    I Friction Coefficient of Marble & Iron on Plastic

    hey, i was looking for information on friction coefficient of marble on plastic and iron on plastic. if you know these values i'll be very glad! thanks in advance
  21. Elementrist

    B Magnetic force driving a small iron ball

    How can I calculate the force from magnetic field of a solenoid, grabbing a small iron ball? I want to use the good old simple F=ma formula in order to calculate the ball's acceleration. But can't find a formula to somehow convert the known field quality (in unit Tesla) to Force (in unit...
  22. D

    I Can iron filings cause permanent eye damage?

    Hey there, how do you dispose of leftover iron filings from an experiment? Can they be disposed of in the normal household waste? Thanks!
  23. G

    A Image Method for B-Field Calculation on Iron Plate

    Hello, I am wondering if it is possible to calculate the B-field of a conductor above an iron plate just using the complex image method. To keep it simple let’s consider a 2D calculation, the metal plate is infinitely deep and wide and the conductor is infinitely long and thin. If the metal...
  24. G

    Exploring Sciency Easter Eggs in Popular Media: From Iron Man 2 to Fallout 4

    Nice little Easter Egg. It’s about one hour and thirteen minutes in. I wonder if there's any comic book cannon about arc reactors having something to do with spacetime?
  25. C

    Permeability of Iron: How Does It Affect Electromagnets?

    I know that iron is typically used in electromagnets to create a stronger magnetic field. But what is the exact nature in which that happens? When it goes in is it slowed down at all while traveling through the metal or does it still keep going at the speed of causality? Also does it have the...
  26. P

    Iron Oxidation States: Fe+2, Fe+3 & Fe- Explained

    I saw on Wikipedia that Fe has both positive and negative oxidation states. I know that Fe will willingly give up its 2 electrons to form an ionic bond with O for example, making it Fe+2. 1. But how can Fe+3 exist? This means it gives up three electrons right? Does this mean the Fe atoms...
  27. W

    Iron and steel industry flows: A question

    Hello, I have a general question for the flows of steel-making up to the casting process. Is the general flow depicted by the image correct? This specific process relies on natural gas reforming to produce H2, which is then used to reduce iron ore. Are there any corrections that I have to make?
  28. yaxlei

    I Why is an iron cover needed for a solenoid?

    Hi everyone, I've heard that it's better to close the "magnetic circuit" of a solenoid by adding a metal casing around the coils, but I don't get why : people say that it's for focusing the magnetic flux lines but how does it increase the force generated by the solenoid ? Thanks if you reply...
  29. K

    Iron block dropped into a container of water sitting on a scale

    Does the scale change during the block sinks? I am so confused... Is there any difference on change of scale with the applying of drag force?
  30. S

    I Are some cosmic rays iron nuclei?

    I had thought that cosmic rays were all protons, but this article says sometimes it's iron. https://getpocket.com/explore/item/let-s-colonize-titan
  31. P

    Ampere's Law for a toroid (finding relative permeability of iron)

    Why is this equation: B(D - d)/mu + Bd = mu0 N I true? B = magnetic field in the hole of the toroid D = Average diameter of the toroid d = Diameter of hole of toroid mu = relative permeability of iron, or whatever the toroid is made of mu0 = 4pi x 10^-7 N = Number of turns on the toroid I =...
  32. Steve Rogers

    B Are silicon iron sheets really necessary for a commercial transformer?

    Hi, everyone. I just finished studying the principle on which a transformer works. It relies on Faraday's law of induction. And my high school physics book uses the following picture for illustration: Roughly speaking, the...
  33. nomadreid

    Does OK hemoglobin make a low level of iron in blood OK?

    Suppose a blood test shows a value of 41 milligrams per deciliter, with a healthy range between 65-175, yet the hemoglobin levels in the same blood test are perfectly normal, as well as are other indicators in the blood test. A doctor explained that one would not need to be worried about the...
  34. BWV

    Sodium Hydroxide + Iron Oxide: Green Tint Explained?

    Was spraying oven cleaner on a somewhat rusted grill and my son, who is taking AP chemistry, asked about the green color that appeared. googled sodium hydroxide + iron oxide and got this FeO + 4NaOH = Na₄FeO₃+ 2H₂O but can't find any info on Na₄FeO₃ - would this have a green tint, and is...
  35. S

    If the lightest metal around were iron, would aerospace even be possible?

    I was reading about an old project I was involved in (X-33), and it got me thinking. It seems that without aluminum (or something as strong per unit mass), modern aerospace vehicles would not be possible. As everyone here knows, the most important design criteria is weight, and iron is much...
  36. BillTre

    Bronze Age or Iron Age? Age of Nebra Sky Disk is disputed

    The age of the Nebra (from Germany) Sky Disk (claimed to be the oldest known representation of the heavens) is in dispute. It was found in the black market, so provenance is unclear. NY Times article here.
  37. Teichii492

    B Can iron form via processes like the r- or s-process?

    Hi, I was wondering by what other methods iron can form in stars? Iron can form during silicon burning and i assume it can also form via the beta- decay of neutron rich isotopes around the iron peak? Are these athe only two processes that relate to the cosmogenesis of iron?
  38. weirdoguy

    Heating up water versus water with an iron brick

    Hi guys, girls, and non-binaries. I'm a private high school teacher and I'm preparing myself to prepare others for polish physics olimpiad. So I delved into books which have a lot of tricky questions and from time to time I stumble upon one I have trouble with. And that's exactly what happened...
  39. Jehannum

    Differentiate between iron and copper sulphide

    I have a quantity of black, lustrous powder taken from inside a gas pipe. I want to know whether it's from copper pipe or from steel pipe. Is there a very simple test I can do? I'm not a chemist and have no specialist equipment.
  40. sekushi0range

    Reason for Ferroin's color shift

    Ferroin is a redox indicator. It is the complexation of phenanthroline and iron. In its reduced state the Fe (II) - phenanthroline complex is red and in its oxidized state the Fe(III)- phenanthroline complex is blue. I am trying to understand in the context of d-d orbital transitions why this is...
  41. K

    Iron (nickel plated) -- what is it?

    I came across the label on a product , that is "Iron (Nickel Plate)" What does it mean? Does it mean it is made of Iron and its surface is nickel plate? What is the general properties of a nickel plate product, can it be understood as a painting on the surface of a material? Does the plate...
  42. TaurusSteve

    Stargazing Wasp-76b is a planet where it rains iron

    https://www.bbc.co.uk/news/science-environment-51828871 "Wasp-76b, as it's known, orbits so close into its host star, its dayside temperatures exceed 2,400C - hot enough to vaporise metals. The planet's nightside, on the other hand, is 1,000 degrees cooler, allowing those metals to condense and...
  43. Thijske

    Kinetic friction coefficient of aluminum on lubricated cast iron

    Hey all, I was recently searching for kinetic friction coefficients, and I noticed that for a reason which is unknown to me, some materials had not been appointed such coefficient. The specific kinetic friction coefficient that I'm looking for is aluminum on greasy/lubricated cast iron. Any type...
  44. J

    Electrical Can I use a 220V Soldering Iron in the US?

    Will 220 volt 50 Hz solder element work in USA?
  45. Osvaldo

    Inserting Stainless steel blades into a Nodular Iron turbine diaphragm

    Would need some advise on how to prevent the blades from melting when pouring the nodular iron into the piece mold. If somebody has experience on the matter or can recommend literature that could help in developing a successful .
  46. A

    Escape velocity of an iron asteroid

    Homework Statement: Jack can jump upwards a distance 1.4 meters when he is on the surface of the Earth. What is his initial velocity when he jumps? Most of the time, however, Jack is in space. He is an asteroid miner: he looks for asteroids made out of useful metals. His job involves landing on...
  47. L

    Engineering Magnetic Field Question (saturating an iron plate)

    I know that the field inside sample is a combination of the demagnetizing field and whatever applied field you may have. So these two fields together influence how big a field you need in order to magnetize the sample.
  48. cynth

    A Electronic band structure of iron superconductor BaFe2As2

    how can I determinate the electronic structure of a multiband system? for example in the case of the superconductor BaFe2As2 , the electronic properties are as known dominated by 5 Fe d states at the fermi energy, so 5 bands cross the Fermi level and form 5 Fermi surface sheets (if we consider...
  49. G

    Magnet's attraction force on a piece of iron

    Hi everyone, Please describe the process accures when placing an iron piece in front of (north pole) natural magnet bar, and how the attraction force is created. Also, to calculate the force magnitude (coulomb law for magnetism formula) how can I determine the piece of iron pole intesity (m)...