How Many Elements in d-Block

Introduction

The periodic table of chemical elements is a combination of rows and columns arrangement. It is known as an icon of chemistry and is widely used in physics, chemistry, and other life sciences. It states the properties of each and every chemical element exhibiting periodic dependence based on their atomic numbers and atomic weights, which is a graphic representation of the periodic law. The periodic table is divided into four rectangular sections called blocks. The columns of the periodic table are called groups and the rows of the periodic table are called periods. The elements from the same group of the periodic table exhibit similar chemical properties.

In this article, we will be discussing the d block of the periodic table. The elements of the d block of the periodic table are: Scandium, Titanium, Vanadium, Gold, Mercury, Actinium, Rutherfordium, Dubnium, Seaborgium, Bohrium, Hassium, Meitnerium, Darmstadtium, Roentgenium, Copernicium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Technetium, Ruthenium, Rhodium, Palladium, Silver, Cadmium, Lanthanum, Hafnium, Tantalum, Tungsten, Rhenium, Osmium, Iridium, Platinum.

The d-block elements are diffusing elements and so, the d stands for "diffuse" and the azimuthal quantum number of d-block elements is 2. It lies in the middle of the periodic table and consists of elements from groups 3 to 12, starting from the fourth period and has a space for 10 d-block elements. As all the d-block elements occupy a transitional zone in characteristics between electropositive elements of groups 1 and 2 and electronegative elements of groups 13 to 16, these elements are called transition elements. Group 3 or group 12 are also considered d-block metals, but sometimes not considered transition elements because they do not show the chemical characteristics of transition metals. For example, multiple oxidation states and coloured compounds of transition elements are not similar to the group 3 and group 12 elements.

The d-block elements have one or more chemically active d-orbital electrons and all are metals because there is a relatively minimal difference in the orbital energies of the different d-orbital electrons. However, the number of electrons involved in chemical bonding may vary. The d-block elements exhibit 2 or more oxidation states. The oxidation states differ by multiples of one, whereas the most common oxidation states are +2 and +3. The lowest formal oxidation numbers can be as low as −4 for the elements chromium, iron, molybdenum, ruthenium, tungsten, and osmium. The highest formal oxidation numbers can be as high as +9 for the element iridium, holding the singular distinction of an oxidation state of +9. The d-orbitals can contain up to 5 pairs of electrons. The first 3 rows of the d-block elements correspond to the 3d, 4d, and 5d orbitals.

Properties of d-block Elements

Ionization Energy of d-Block Elements: Ionization energy is the energy required to remove the outermost valence electron from an atom/ion. It is the force of attraction on the outermost electron. And hence, the larger the nuclear charge on the atom and the smaller the radii of the electron, the larger will be the ionisation energy of the element (IE). Ionization Energy will be more for the half-filled and fully-filled orbitals of elements. The Ionization Energy (IE) of the d-block elements is larger than the s-block and smaller than the p-block elements. The ionisation energy of d-block elements increases with the increase in atomic number up to the element Iron (Fe).

Metallic Character of d-Block Elements: The metallic character of the d-block element shows typical metallic behaviour of malleability, high tensile strength, ductility, electrical and thermal conductivity, and metallic lustre. These elements are very hard and have a high enthalpy of atomization and low volatility. The hardness of d-block elements increases with the number of unpaired electrons in the atom.

Oxidation States of d-Block Elements: The oxidation state is considered a hypothetical state, where the atom releases or gains electrons more than the usual valency state. It is useful in describing the properties of the atom/ion. Transition elements can have electrons in both s and d-orbitals since the energy difference between s-orbital and d-orbital is very small, and so both electrons can be involved in ionic and covalent bond formation. They exhibit multiple valency states or oxidation states. Each element in the d-orbital exhibits a minimum oxidation state corresponding to the number of s-electrons and exhibits a maximum oxidation state corresponding to the total number of electrons available in both s and d-orbitals.

Electrode Potential in d-Block Elements: The relative stabilities of d-block metal ions in different oxidation states in the aqueous medium is predicted using electrode potential data. The more the negative electrode potential, the higher the stability of the metal ions.

Density in d-Block Elements: The density of the d-block elements is inversely proportional to atomic radii. Among the transition metal series, the density decreases with an increase in atomic radii. The density decreases over the period. The periodic column density of the 4d series is larger than 3d, due to a larger decrease in atomic radii and lanthanide contraction and hence, the volume density of 5d series transition elements is larger than the 4d series.

Catalytic Activity in d-Block Elements: The transition elements can act as good catalysts due to the presence of vacant d-orbitals. They have a tendency of exhibiting variable oxidation states and form reaction intermediates with reactants. Also, these elements have defects in their crystal lattices.

Conclusion

To conclude, there are 40 elements present in the d-block of the periodic table. These elements and their alloys play a fundamental role in the existence of life. The d-block metals and their alloys have great importance in shaping the Iron Age, Bronze Age, and most importantly the steel age. The industrial uses of the d-block elements are iron and its amalgam, steel, and titanium for the manufacture of airships and spaceships. Tungsten is used in making electrical fibres and bulbs.