What is Iron?

Maram Ghadban, Laura Foist
  • Author
    Maram Ghadban

    A freelance tutor equipped with a bachelor's of science in chemical engineering. Graduated from the American University of the Middle East with a GPA of 3.87, performed a number of scientific primary and secondary research. Tutored university level students in various courses in chemical engineering, math, and art. Has experience tutoring middle school and high school level students in science courses.

  • Instructor
    Laura Foist

    Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

Learn about iron compounds and their uses. Explore chemical formula and chemical name of common iron compounds, and the uses of iron, such as for plants. Updated: 11/16/2021

Table of Contents


Iron Compounds

Iron makes up much of earth's inner and outer core. In fact, 5% of the earth's crust is made of iron! The most common rocks that contain iron are:

  • Hematite {eq}Fe_2O_3 {/eq}.

Figure 1: Hematite

Iron on earth

  • Greenalite {eq}(Fe^{+2},Fe^{+3})_{2-3}Si_2O_5OH_4 {/eq}.
  • Magnetite {eq}Fe_3O_4 {/eq}.

Figure 2: Magnetite

Iron on earth

  • Taconite, which are pellets of low-grade iron ore.

Not only is iron a common substance on earth but also abundantly available in the sun and stars. Iron fragments were deposited on earth when a dying star erupted massively many billions of years ago. Now, what is iron? Is iron a molecule? A chemical substance? Is iron a compound?

Figure 3: Iron is an element

Iron is an element from the periodic table

Iron is a lustrous gray metal that is found in group number 8 and period 4 on the periodic table. Iron's chemical name is ferrum, from the Latin word ferrium. This is how iron got Fe as its symbol. The format of nonmetal elements formula with iron is Fe X, where X is a nonmetal element or compound. The number of protons in iron's nucleus is 26, which makes its atomic number also 26. Its electron configuration is {eq}[Ar] 3d^6 2s^2 {/eq}. There are six electrons in its d orbital and two electrons in the s orbital, that means its outermost shell has a total of eight electrons. Notice that the d orbital is partially filled. They normally can hold a total of ten electrons, but the d orbitals in iron only hold six electrons. This is a good enough indication to tell that iron is a transition metal. Iron is categorized according to its oxidative state into:

  • Ferrous compounds ({eq}Fe^{+2} {/eq}), also known as bivalent iron (II) compounds.
  • Ferric compounds ({eq}Fe^{+3} {/eq}), also known as trivalent iron (III) compounds.

Ferric and ferrous are the major types of iron compounds. Before proceeding to the sections that provide more information about these compounds, the reader is advised to examine the table that documents many of iron's important properties.

Parameter Data
Physical State Solid at room temperature
Boiling Point 2861C
Melting Point 1538C
Density 7.874 g/cm3
Oxidative State +2,+3
Atomic Mass 55.845u

Ferrous Compounds

As mentioned in the earlier section, the type of iron compound is dependent on the oxidative state of iron itself. The oxidative state is an atom's oxidation number, which is a number that refers to the number of electrons an atom gains or loses, when it forms chemical bonds with other atoms. The type of chemical bond such atoms form is an ionic bond, which involves the complete transfer of one or more electrons from one atom to another. An electrostatic attraction is formed when ions form these bonds. The ion that has the ability to liberate the electrons from its outermost shell is called cation. And the ion that has the ability to accept the electrons are called anions. Cations are positively charged ions; they have more protons than they do electrons. Anions are negatively charged ions; they have more electrons than they do protons. Figure 4 shows how ionic bonds are formed through the complete transfer of electrons from the cation to the anion.

Figure 4: How ionic bonds are formed

Ionic bonds

Iron has a variable oxidative state; its oxidation number can be +2 or +3 depending on the compound it's going to form. The reason why this element has multiple oxidation numbers is because it is a transition metal. In the case of ferrous compounds, the oxidation number of iron is +2. {eq}Fe^{+2} {/eq} is known as the ferrous cation. This means iron must transfer two of its electrons to another element/compound when it forms ferrous compounds. Ferrous compounds are known to have a pale green shade. The following is a list of ferrous compounds:

  • Ferrous oxide\iron (II) oxide {eq}FeO {/eq}: {eq}cation \: Fe^{+2} \: anion \: O^{-2} {/eq}
  • Ferrous phosphate\iron (II) phosphate {eq}Fe_3 (PO_4 )_2 {/eq}: {eq}cation \: Fe^{+2} \: anion \: PO_4^{-3} {/eq}.
  • Ferrous nitrate\iron (II) nitrate: {eq}Fe (NO3 )_2 {/eq}: {eq}cation \: Fe^{+2} \: anion \: NO_3^{-1} {/eq}.
  • Ferrous sulfate\iron (II) sulfate {eq}FeSO_4 {/eq}: {eq}cation \: Fe^{+2} \: anion \: SO_4^{-2} {/eq}.
  • Ferrous chloride\iron (II) chloride {eq}FeCl_2 {/eq}: {eq}cation \: Fe^{+2} \: anion \: Cl^{-1} {/eq}.

Ferric Compounds

When iron's oxidative state is +3, it gives up three of its outermost electrons to form ferric compounds. The iron ions in these compounds are called ferric cations. The color of ferric compounds tend to be brownish or rust-like. The following is a list of ferric compounds:

  • Ferric chloride\iron (III) chloride {eq}FeCl_3 {/eq}: {eq}cation \: Fe^{+3} \: anion \: Cl^{-1} {/eq}.
  • Ferric oxide\iron (III) oxide {eq}Fe_2O_3 {/eq}: {eq}cation \: Fe^{+3} \: anion \: O^{-2} {/eq}.
  • Ferric sulfate\iron (III) sulfate {eq}Fe_2(SO_4)_3 {/eq}: {eq}cation \: Fe^{+3} \: anion \: SO_4^{-2} {/eq}.
  • Ferric phosphate\iron (III) phosphate {eq}FePO_4 {/eq}: {eq}cation \: Fe^{+3} \: anion \: PO_4^{-3} {/eq}.

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Frequently Asked Questions

What are the uses and applications of iron?

Iron is used in construction, pharmaceuticals, agriculture, and water treatment. It is used in the manufacturing of many types of alloy steels and stainless steels, which are used in buildings, industrial plants, and in construction. Some iron compounds are used in sewage water treatment and in water purification.

Is iron a compound or not?

Iron by itself is not a compound, it is an element. Iron can form various compounds. The types of compounds iron makes depends on its oxidative state. If its oxidation number was +2 then it makes ferrous compounds. If its oxidation number was +3 then it makes ferric compounds.

What is the element name of Fe?

The name of the element with the chemical symbol Fe is iron. The symbol Fe is derived from its Latin name, Ferrium. Iron is a transition metal in group 8 and period 4 on the periodic table.

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