D Block Elements or Transition Elements Electronic Configurations
Groups 3 to 12 elements are called d-block or transition elements. These elements are present between p-block and s-block elements in the periodic table. These elements’ properties are intermediate between the properties of s -block and p -block elements, i.e. d -block elements represent a change or transition in properties from most electropositive s - block elements to less electropositive p - block elements. Therefore, these elements are called transition elements.
The d-block elements include the most common metals used in construction and manufacturing, metals that are valued for their beauty (gold, silver and platinum), metals used in coins (nickel, copper) and metals used in modern technology (titanium).
In the transition element, the last differentiating electron is accommodated on penultimate d-orbitals, i.e., d-orbitals are successively filled. The general electronic configuration of transition elements is:
(n-1)1-10 ns 0,1 or 2
There are four complete rows (called series) of ten elements each corresponding to filling of 3d, 4d, 5d and 6d-orbitals respectively. Each series starts with a member of group third (IIIB) and ends with a member of group twelve (IIB).
👉 After taking the JEE Main exam, you can predict your rank using our JEE Main Rank Predictor 2024.
Why are D-block elements also referred to as Transition elements (In Brief)?
Groups 4-11 are made up of transition components. Transition elements include scandium and yttrium from Group 3, which have a partly filled d subshell in the metallic form. Elements in the 12 columns of the d block, such as Zn, Cd, and Hg, have entirely filled d-orbitals and are hence not considered transition elements.
Transition Elements get their name from the fact that they are placed between s and p block elements and have characteristics that transition between them. So, while all transition metals are d block elements, they are not all transition elements. Filling Transition Metal Orbitals
The first-row transition metal electron configuration consists of 4s and 3d subshells with a core of argon (noble gas). This applies only to transition metals in the first row, adjustments are required when writing the electron configuration for the other transition metal rows. Before the first row of transition metals, the noble gas would be the core written around the element symbol with brackets (i.e. Ar-Ar would be used for the first row of transition metals), and the electron configuration would follow an Ar-Ar nsxndx format. The electron configuration for first-row transition metals would simply be Ar-Ar 4sx3dx. Based on the periodic table, the energy level, "n," can be determined simply by looking at the row number in which the element is located. There is, however, an exception for the d-block and f-block, where the energy level, "n" for the d-block is "n-1" ("n" minus 1) and "n-2" for the f-block (see the following periodic classification table). The "x" in nsx and ndx, in this case, is the number of electrons in a particular orbital (i.e. s - orbitals can hold up to 2 electrons, p - orbitals can hold up to 6 electrons, d - orbitals can hold up to 10 electrons, and f - orbitals can hold up to 14 electrons). To determine what "x" is, simply count the number of boxes you will find before you reach the element you are trying to determine the configuration of the electron.
First transition or 3d-series:
Elements: Sc(21) to Zn(30). 3d-orbitals are gradually filled up.
The actual configurations are explained on the basis of the stability concept of half-filled or completely filled (n-l) d-orbitals. (n-l) d-subshell is more stable when 5 or 10 electrons are present, i.e., every d-orbital is either singly occupied or doubly occupied.
Second Transition or 4d-series
This series consists of elements from Y(39) to Cd(48). 4d-orbitals are gradually filled up.
Elements marked with an asterisk have anomalous configurations. Nuclear-electron and electron-electron forces are attributed factors.
Third Transition or 5d-series:
This series consists of elements from La(S7) to Hg(80) except 14 elements of lanthanide series from Ce(S8) to Lu(71). 5d-orbitals are gradually filled up.
Fourth Transition or 6d-series
This series consists of elements from Ac(89) to Uub(112) except 14 elements of the actinide series from Th(90) to Lr(103). 6d-orbitals are gradually filled up.
Properties of D Block Elements
Ionization Energy of D Block Elements:
Ionisation energy is the energy required to take away the outermost electron from an atom or ion. It depends on how strongly the nucleus attracts the electron. If the nucleus has a higher charge and the electron is closer, the ionization energy is higher. For D block elements, the ionization energy is greater than for s-block elements but less than for p-block elements. Half-filled and fully-filled orbitals also increase ionization energy.
In the first series of D block elements, except for chromium and copper, the first ionization energy involves removing an electron from the filled s-orbital. In Co and Ni, the sharing of d-electrons decreases ionization energy. Copper and zinc, as s-block elements, show increasing ionization energy. In the second series, elements from Niobium show a gradual increase in ionization energy with atomic number. Palladium, with a completed d-shell, has the highest ionization energy.
Due to lanthanide contraction, the nuclear charge attracts electrons more strongly, making the ionization energy of 5d elements larger than 4d and 3d. In the 5d series, all elements except Pt and Au have a filled s-shell. Elements from Hafnium to rhenium have the same ionization energy, and it increases afterward, with Iridium and Gold having the maximum ionization energy.
Metallic Character:
D block elements display typical metallic characteristics such as high tensile strength, malleability, ductility, electrical and thermal conductivity, metallic shine, and the ability to crystallize in various structures. These elements are generally hard and have a high enthalpy of atomization and low volatility, except for copper. The hardness increases with the number of unpaired electrons. Therefore, chromium (Cr), molybdenum (Mo), and tungsten (W) are among the hardest metals in the D block. However, the elements in group - 12 (zinc, cadmium, and mercury) deviate from this trend.
Oxidation States of D Block Elements
The oxidation state is like a make-believe condition where an atom seems to either give away or grab more electrons than it usually does. This concept helps us understand how atoms or ions behave. When it comes to transition elements or ions, they can have electrons in both s and d-orbitals.
Because there's not much energy difference between s and d-orbitals, electrons from both can get involved in forming bonds - either ionic or covalent. This leads to these elements showing different possible oxidation states (valency states).
So, each transition element can show the smallest oxidation state based on the number of s-electrons it has and the largest oxidation state based on the total number of electrons in both s and d-orbitals. In between these extremes, there are also other possible oxidation states.
Trends in the Oxidation States
Certain elements like Cr, Cu, Ag, Au, and Hg have a minimum oxidation state of 1.
The stability of oxidation states follows a pattern: 3d series elements are most stable in +2, 4d series in +2 and +4, and 5d series in +4. Some higher oxidation states of 3d elements are not stable, leading to reactive compounds. Meanwhile, higher oxidation states of 4d and 5d elements are stable, resulting in unreactive compounds.
Elements with high oxidation numbers tend to form oxides and fluorides, not bromides and iodides. For example, vanadium forms VO4–, CrO42-, MnO4–, VF5, VCl5, VBr3, VI3 but not VBr5, VI5.
Middle-order elements in each series exhibit the maximum oxidation state equal to the sum of s and d-electrons. Examples include manganese in the 3d series with a +7 oxidation state.
Elements can display oxidation states ranging from the minimum to the maximum.
Lower oxidation states result in ionic and basic compounds, in-between states are amphoteric, and higher oxidation states lead to covalent and acidic compounds.
Lower oxidation states can be stabilized by back bonding in complexes, as seen in Ni(CO)4, Fe(CO)5, [Ag(CN)2]–, and [Ag(NH3)2]+.
The stability of oxidation states depends on factors like orbital stability, ionization energy, electronegativity, enthalpy of atomization, and enthalpy of hydration. For example, Ni2+ compounds are more stable than Pt2+, while Pt4+ compounds are more stable than Ni4+ due to ionization energies.
In p-block elements, heavier elements prefer lower oxidation states due to the inert pair effect. However, in d-block elements, higher oxidation states are more stable for heavier members in a group.
Electrode Potential in D Block Elements
Water contains transition metals in stable oxidation states. The greater the negative (or less positive) value for ΔH(ΔHsub + lE + ΔHhyd) or E°, the more stable the cation's oxidation state.
E° decreases in value, indicating that the decreased condition is more stable. Transition elements have lower E° values than metals in the first and second groups.
Physical Properties of D Block Elements
Density: In the transition series, density follows the opposite trend of atomic radii. It increases initially and then decreases along the period.
In the 4d series, density is higher than in the 3d series due to lanthanide contraction and a significant decrease in atomic radii. The volume density of 5d series transition elements is double that of 4d series.
In the 3d series, scandium has the lowest density, and copper has the highest. Osmium and iridium of the 5d series have the highest density among all d block elements.
Some relative radii of d block elements are Fe < Ni < Cu, Fe < Cu < Au, Fe < Hg < Au.
Why Do D Block Elements Have High Melting and Boiling Points?
D block elements have high melting and boiling points due to unpaired electrons and partially filled d-orbitals. This leads to strong covalent and metallic bonding, especially until the d5 configuration. The trend reverses as more electrons pair up in the d-orbital.
Cr, Mo, and W have the highest melting and boiling points in their series.
Manganese (Mn) and Technetium (Tc) with half-filled configurations have unusually low melting and boiling points.
Group 12 elements (Zn, Cd, and Hg) have no unpaired d-electrons, resulting in the lowest melting and boiling points in their series.
Mercury - the Liquid Metal:
Mercury is unique because it's the only metal that's a liquid at room temperature. This is because the 6s valence electrons of Mercury are more tightly held by the nucleus (due to lanthanide contraction), causing them to be less involved in metallic bonding.
Which Transition Elements Are Noble Metals?
In the three transition series,
As you move from left to right in the 3d series to the right corner where 5d transition elements are located, various properties change. The density, electronegativity, and electrical and thermal conductivities increase, while the enthalpies of hydration of metal cations decrease. This shift indicates that transition metals become less reactive and more "noble" as you go towards the lower right corner of the d block. Metals like Pt and Au in this region are so unreactive that they're often called "noble metals."
(Image will be Uploading Soon)
Magnetic Properties of d Block Elements
Materials can be categorised based on their interaction with a magnetic field:
Diamagnetic: Repelled by the magnetic field.
Paramagnetic: Attracted to the magnetic field.
Ferromagnetic: Can retain a larger magnetic nature even in the absence of a magnetic field.
Diamagnetism is caused by paired electrons, paramagnetism by unpaired electrons aligned together, and ferromagnetism by unpaired electrons contributing to orbital and spin magnetic moments. The 3d series has negligible orbital angular momentum, and the spin-only magnetic moment is given by the formula,
µ = √[n(n+1)] BM,
where 'n' is the number of unpaired electrons.
BM - is a Bohr Magneton unit
Chromium and molybdenum have the maximum number (6) of unpaired electrons and magnetic moment.
The table shows the magnetic properties of ions of d block elements, including their outer configuration, number of unpaired electrons, and observed and calculated magnetic moments.
Formation of Coloured Ions by d Block Elements
Compounds of d block elements exhibit various colors because they can absorb light frequencies in the visible region. When these elements absorb light, the transmitted light shows a color complementary to the absorbed frequency, resulting in the observed color of transition element compounds.
d-d Transition:
Sometimes, electrons in certain materials get excited to higher energy levels, making the material show colors.
In transition metal ions, this color change happens due to a process called d-d transition.
The d-orbitals, which are like energy levels for electrons, usually have the same energy. When other molecules bond with the metal, it splits these orbitals into two groups, eg and t2g.
The difference in energy (∆E) between these groups depends on how strongly the bonding molecules are attached.
When light in the visible range (400-700nm) hits these metal ions, electrons move from lower to higher d-orbitals, absorbing the light energy and showing a color complementary to it.
For example, copper ions look blue-green because they absorb red light.
Color Variation:
The color of metal ions can change based on their oxidation state (like how much they've given or taken electrons).
It also depends on the molecules they're bonded with. For instance, copper ions look light blue with water but deep blue with ammonia.
Metal ions with full or empty d-orbitals are usually colorless.
Ligand-Metal Bonding:
Molecules called ligands can share their electrons with metal ions, creating a bond known as ligand-metal or dπ – pπ bonding.
This interaction can also give color to compounds.
In simpler terms, the color of certain materials changes because their electrons get excited to different energy levels or due to how they interact with other molecules. This is why we see different colors in transition metal compounds.
D Block Elements and Complex Compounds
D block elements, which include transition metals, have a tendency to form complex compounds. These compounds occur when a metal binds with neutral molecules or anions. Transition metals, found in the d block, are especially good at forming these complexes due to their small size, high charge, and the availability of d orbitals for bonding.
Transition metals can attract electrons and accept lone pairs from other molecules, forming what's called coordinate bonding. They often create complex molecules with various substances like CO, NO, NH3, H2O, F–, Cl–, and CN–. Examples of such complexes include [Co(NH3) 6] 3+, [Cu(NH3)4] 2+, [Fe(CN)6]4−, [FeF6] 3−, [Ni(CO)4].
Catalytic Activity of D Block Elements
D block elements, especially transition metals in their ionic form, play a crucial role as catalysts in many chemical and biological reactions. Catalysts are substances that speed up reactions without being consumed.
Examples of d block metal catalysts include iron in Haber's process for making ammonia, vanadium pentoxide in sulfuric acid manufacture, titanium chloride as a Zigler Natta catalyst in polymerization, and palladium chloride in converting ethylene to acetaldehyde.
Why are D Block Elements Good Catalysts?
Vacant d-orbitals: Transition metals have empty d orbitals that facilitate bonding with other molecules.
Variable oxidation states: These elements can easily change their oxidation states during a reaction, making them versatile in catalysis.
Formation of reaction intermediates: Transition metals tend to form intermediate compounds during reactions, aiding in the overall process.
Defects in crystal lattices: The presence of defects in their crystal structures enhances catalytic activity.
Variable Oxidation State of D-block Elements
The oxidation state is a notional condition in which the atom seems to lose or gain more electrons than it does in its normal valency state. It's still useful for understanding the atom's characteristics. Both s and d-orbitals can have electrons in transition elements.
Because the energy difference between the s and d orbitals is modest, both electrons can participate in the production of ionic and covalent bonds, resulting in multiple(variable) valency states (oxidation states).
As a result, any transition element can have a minimum oxidation state equal to the number of s-electrons and a maximum oxidation state equal to the total number of electrons in both s and d-orbitals. Between oxidation states, new oxidation states become feasible.
Transition Elements Make Reactions More Efficient by:
Providing a large surface area for absorption, allowing enough time for the reaction.
Interacting with reactants through their empty orbitals.
Actively participating in redox reactions through their multiple oxidation states.
Alloy Formation in Transition Elements
Transition elements in a series have similar atomic sizes, making it easy for them to replace each other in a solid solution known as an alloy. Alloys are mixtures of two metals or a metal with a non-metal. They are hard and have high melting points compared to the original metal. For example, steel is an alloy of iron with metals like chromium and vanadium.
Interstitial Compounds of Transition Elements
Transition metals have gaps in their crystal lattice, and small non-metallic atoms or molecules like hydrogen and carbon can fill these gaps, forming interstitial compounds. These compounds have high melting points, are very hard, conduct electricity similarly to other metals, and are chemically inert. Examples include TiC and Fe3H.
Non-Stoichiometric Compounds
Compounds of transition metals may have varying oxidation states and can exist together without a specific composition or structure. This behavior is especially observed when combined with group 16 elements like oxygen and sulfur. Examples include $Fe_{0.94}O$ and $VSe_{0.98}$.
Important Compounds of Transition Elements
Some crucial compounds of transition elements include:
Potassium Dichromate (K2Cr2O7): Used in the leather industry and as an oxidizing agent in azo compound preparation. It has a unique structure with a strong oxidizing ability.
Potassium Permanganate (KMnO4): Known for its intense purple color, KMnO4 is used as an oxidant in organic chemistry, bleaching textiles, and decolorizing oils due to its strong oxidizing properties. It exhibits diamagnetic and weak paramagnetic properties based on temperature.
Conclusion
Mastering D Block Elements is crucial for JEE Main success. These elements, found in the middle of the periodic table, showcase diverse properties and applications. Understanding their unique electronic configurations, oxidation states, and complex compounds is vital. The transition metals within this block play key roles in catalysis, industry, and biological processes. For JEE Main aspirants, a solid grasp of D Block Elements opens doors to scoring well in inorganic chemistry. Regular practice, focusing on trends, and linking concepts will empower you to tackle questions effectively and shine in the JEE Main examination.
JEE Main Chemistry Chapter-wise Solutions 2023-24
Important Related Links for JEE Main 2023-24
FAQs on Electronic Configurations of D Block Elements
1. What is the electronic configuration of D-Block Elements?
The electrical configuration of D block elements is (n-1)d 1-10ns 1-2. Half-filled orbitals and filled d orbitals are both stable for these elements. The electronic configuration of chromium, which includes half-filled d and s orbitals in its configuration – 3d54s1, is an example of this. Another example is the electrical configuration of copper. Copper has a 3d104s1 electronic setup rather than a 3d94s2. According to the Aufbau principle and Hund's rule of multiplicity, electrons are added to the 3d subshell from left to right along the period.
2. Why do elements in d-block have a varying range of oxidation states?
The large variety of oxidation states (oxidation numbers) that transition metals may exhibit is one of their most notable characteristics. Because the 4s and 3d sublevels are so near in energy, variable oxidation states are feasible. Either of these sublevels is quite easy to lose electrons from.
However, to say that only transition metals may have different oxidation states is incorrect. Sulphur, nitrogen, and chlorine, for example, have a very wide variety of oxidation states in their compounds and are not transition metals.
3. From where students can access detailed information about d-block elements?
Vedantu is the right place for all of your queries and provides you best solution regarding your search for d-block elements. The experts have explained the topic in a very detailed and organised manner. It will help students in preparing for their respective competitive exams and enable students to get fluent with in-organic chemistry. D-block elements are one of the most important topics in Class 11 and 12 Chemistry. Vedantu’s advantage can help students to learn and understand the topic in-depth with ease and comfort.
4. What makes transition metals colourful?
Partially filled (n-1)d orbitals are associated with a coloured transition element compound. Unpaired d-electrons in transition metal ions undergo the electronic transition from one d-orbital to another. During the d-d transition, electrons absorb a portion of the radiation's energy and release the rest as coloured light. The colour of an ion is the opposite of the colour it absorbs. As a result, coloured ions are generated as a result of the d-d transition, which is evident for all transition elements.
5. Does d-block contain any non-metallic element?
All of the elements in the d-block are metals, and the majority of them have one or more chemically active d-orbital electrons. The number of electrons engaging in chemical bonding might vary due to the minor variation in energy between the different d-orbital electrons. The elements in the d-block tend to have two or more oxidation states that differ by multiples of one. +2 and +3 are the most prevalent oxidation states. Chromium, iron, molybdenum, ruthenium, tungsten, and osmium have oxidation numbers as low as 4, whereas iridium has the unique ability to achieve an oxidation state of +9.
