This series contains elements from atomic number 21 (scandium) to atomic number 30 (Zinc). It is called 3d series because last electron goes in 3d orbital. It is present in fourth period of Periodic Table.

Scandium is a rare element that exists in compounds mainly in the +3 oxidation state— for example, in ScCl₃, Sc2O₃, and Sc₂(SO₄)₃. The chemistry of scandium strongly resembles that of the lanthanides, with most of its compounds being colorless and diamagnetic.

Titanium is widely distributed in the earth’s crust (0.6% by mass). Because of its relatively low density and high strength, titanium is an excellent structural material, especially in jet engines, where light weight and stability at high temperatures are required.

In addition, the resistance of titanium to chemical attack makes it a useful material for pipes, pumps, and reaction vessels in the chemical industry.

Rutile is processed by treatment with chlorine to form volatile TiCl₄, which is separated from the impurities and burned to form TiO₂.

Vanadium is widely spread throughout the earth’s crust (0.02% by mass). It is used mostly in alloys with other metals such as iron (80% of vanadium is used in steel) and titanium.

Vanadium(V) oxide (V₂O₅) is used as an industrial catalyst in the production of materials such as sulfuric acid.

Chromium: Although chromium is relatively rare, it is a very important industrial material. The chief ore of chromium is chromite (FeCr2O4), which can be reduced by carbon to give ferrochrome,

FeCrO₄ (s) + 4C → Fe (s) + 2Cr (s) + 4CO (g)

Which can be added directly to iron in the steel making process.

Manganese can exist in all oxidation states from +2 to + 7, although +2 and +7 are the most common.

Manganese(II) forms an extensive series of salts with all the common anions. Table 17 shows some compounds of Manganese in its most common oxidation states.

Cobalt is a hard, bluish white metal mainly used in alloys such as stainless steel and stellite, an alloy of iron, copper, and tungsten that is used in surgical instruments.

The chemistry of cobalt involves mainly its +2 and +3 oxidation states, although compounds containing cobalt in the 0, 1, or 4 oxidation state are known.

Nickel, which ranks twenty-fourth in elemental abundance in the earth’s crust, is found in ores, where it is combined mainly with arsenic, antimony, and sulfur.

Nickel is also widely used in the production of alloys such as steel.

Nickel in compounds is almost exclusively in the +2 oxidation state.

Magntetic properties of transition metals

There are various substances which show magnetic behaviour. We have substances that are attracted by the magnetic field and are called paramagnetic. This phenomenon is called paramagnetism. Paramagnetic property is only shown when the substance contains one or more unpaired electrons. When a substance acquires a permanent magnetic moment, it is known as ferromagnetic and the phenomenon is called ferromagnetism. substance shows diamagnetism when it contains only paired electrons.

Most of the transition elements show paramagnetic behaviour. The unpaired electrons in (n-1) d-orbitals are responsible for the magnetic properties. The paramagnetic character of the transition metals increases on moving from left to right as the number of unpaired electron increases from one to five. The middle elements are found to possess the maximum paramagnetic property. The magnetic properties decrease with the decrease in the number of unpaired electrons.