Definition: What are transition metals?

Transition metals are a group of metals in the middle of the periodic table that have some similar properties to one another. A unique feature of these metals is that they have valence electrons in two shells, and electrons from both these shells participate in chemical bonding. As a result, they show several common oxidation states ^[1].

For inner transition metals, refer to lanthanide and actinide.

Where are transition metals located in the periodic table?

The transition metals are located in the middle of the periodic table in between the elements of the left and the right. They act as a bridge or transition between the two sides of the periodic table. They are also called d-block elements since they occupy the space between the s-block and the p-block elements of the periodic table and have their d orbitals filled progressively. They range from Group 3 (IIIb) to Group 12 (IIb) with a general configuration given by (n-1)d^1-10ns^1,2. Although in d-block, scandium and zinc are not considered transition metals because their stable ions do not have any d electrons to form complex compounds ^{[2, 3, 4]}.

List of Transition Metals [5]
Element	Symbol	Atomic Number
Titanium	Ti	22
Vanadium	V	23
Chromium	Cr	24
Manganese	Mn	25
Iron	Fe	26
Cobalt	Co	27
Nickel	Ni	28
Copper	Cu	29
Yttrium	Yt	39
Zirconium	Zr	40
Niobium	Nb	41
Molybdenum	Mo	42
Technetium	Tc	43
Ruthenium	Ru	44
Rhodium	Rh	45
Palladium	Pd	46
Silver	Ag	47
Cadmium	Cd	48
Hafnium	Hf	72
Tantalum	Ta	73
Tungsten	W	74
Rhenium	Re	75
Osmium	Os	76
Iridium	Ir	77
Platinum	Pt	78
Gold	Au	79
Mercury	Hg	80
Rutherfordium	Rf	104
Dubnium	Db	105
Seaborgium	Sg	106
Bohrium	Bh	107
Hassium	Hs	108
Meitnerium	Mt	109
Darmstadtium	Ds	110
Roentgenium	Rg	111
Copernicium	Cn	112

Common Properties and Characteristics of Transition Metals

The transition metals are very hard and heavy. They are classified into the 1^st, 2^nd, and 3^rd transition series, with elements across the 1^st series (Ti to Cu) showing similar physical and chemical properties. This is due to the small difference in the effective nuclear charge of these elements as a result of the shielding of the 4s electrons by the filling 3d electrons ^[6].

Physical Properties of Transition Metals ^{[5, 6]}

• Shiny and silvery
• High density
• High melting and boiling points
• Good conductors of heat and electricity, especially copper and silver
• Gold and silver are malleable, while copper is very ductile

Chemical Properties of Transition Metals ^{[5, 6, 7]}

• Less reactive than alkali metals
• Display several oxidation states ^[7]
• Have a tendency to form colored ions and compounds (e.g. CuSO₄ is a blue crystal)
• Form stable complex compounds with other elements (e.g. halides such as FeCl₂, NiCl₂)
• Form positively charged molecular complexes with other atoms (e.g. CrO₄^2-)
• Iron and titanium react with oxygen to form oxides

Magnetic Properties of Transition Metals ^[8]

• Iron, nickel, and cobalt show magnetic behavior up to a certain temperature
• Iron is ferromagnetic up to 770 °C (Curie point), beyond which it is paramagnetic, i.e. weakly attracted to a magnetic field
• Nickel loses its ferromagnetic properties at its Curie temperature of 355 °C
• Cobalt is ferromagnetic until it becomes paramagnetic at its Curie temperature of 1115 °C

Why are transition metals colored?

Colors in transition metals are due to electron transition, namely charge transfer transition and d-d transition. A charge transfer transition occurs when the metal is in a high or low oxidation state, during which charge is transferred between the metal and a nonmetal species (ligand). In the d-d transition, an electron moves from one d orbital to another. In complexes of transition metals, these d orbitals have different energies. When white radiation falls in these complex compounds, the d electron absorbs some radiation, and the rest is transmitted. Color is perceived as the radiation transmitted by these compounds ^[9].

List of colors of transition metal ions and ion complexes [10]
Transition metal ion	Color
Fe3+	Brown to yellow
Co2+	Pink
Cu2+	Blue-green
Ni2+	Bright green
Fe2+	Olive green
Ti3+	Purple
Cr3+	Violet
Mn2+	Pale pink
CrO42-	Orange
Cr2O72-	Yellow

Where are transition metals found?

Certain transition metals like iron, copper, titanium, and mercury can be found in the earth’s crust, with iron being the most abundant. Copper can also be found on the surface of the earth and has been used for making useful tools since ancient times ^[11].

Uses and Application of Transition Metals

Transition metals have a wide variety of applications ^[12].

• Iron is used in steel which is a construction material in buildings, ships, vehicles, etc.
• Alloys of titanium are used in aircraft and in artificial knee and hip joints.
• Copper, being ductile and conducting, is used to make electrical wires and water pipes.
• Nickel and chromium are used in stainless steel, which is practically found in every kitchen item. Chromium, particularly, is responsible for the shiny color of stainless steel.
• Zinc is used as an anti-corrosion coating in galvanized steel.
• Cobalt is used in magnetic alloys and also in engines and jet turbines.
• Gold and silver are used in jewelry. Silver is also used in making dishes (silverware) and in many electronic applications.
• Platinum is used in jewelry, thermometers, catalytic converters, and rocket engines.
• Manganese and vanadium are added to steel to make it wear-resisting.

References

1. Definition of transition metals – Britannica.com
2. Location of transition metals in periodic table – Chemed.chem.purdue.edu
3. List of transition metals – Coolperiodictable.com
4. List of transition metals – Toppr.com
5. Table of transition metals – Study.com
6. Properties of transition metals – Chem.libretexts.org
7. Chemical properties of transitional metals – Chem.libretexts.org
8. Magnetic properties of transition metals – Courses.lumenlearning.com
9. Color of transition metals – Chemistry.stackexchange.com
10. Table of colors – Thoughtco.com
11. Availability of transition metals – Scienceclarified.com
12. Applications of transition metals – Schooledbyscience.com