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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). 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. Element Symbol At. No. Electronic Configuration Scandium Sc 21 Ar-Ar 3d142 Titanium Ti 22 Ar-Ar 3d242 Vanadium V 23 Ar Ar 3d342 Chromium Cr 24 Ar-Ar 3d541 Manganese Mn 25 Ar-Ar 3d542 Iron Fe 26 Ar-Ar 3d642 Cobalt Co 27 Ar-Ar 3d742 Nickel Ni 28 Ar-Ar 3d842 Copper Cu 29 Ar-Ar 3d1041 Zinc Zn 30 Ar-Ar 3d1042
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. Element Symbol At. No. Electronic Configuration Yttrium Y 39 Kr Kr 4d1 5s2 Zirconium Zr 40 Kr Kr 4d2 5s2 Niobium Nb 41 Kr Kr 4d4 5s1 Molybdenum Mo 42 Kr Kr 4d5 5s1 Technetium Tc 43 Kr Kr 4d6 5s2 Ruthenium Ru 44 Kr Kr 4d7 5s2 Rhodium Rh 45 Kr Kr 4d8 5s1 Palladium Pd 46 Kr Kr 4d10 5s0 Silver Ag 47 Kr Kr 4d10 5s1 Cadmium Cd 48 Kr Kr 4d10 5s2
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.
Element Symbol At. No. Electronic Configuration Lanthanum La 57 Xe Xe 5d1 6s2 Hafnium Hf 72 Xe Xe 4f14 5d2 6s2 Tantalum Ta 73 Xe Xe 4f14 5d3 6s2 Tungsten W 74 Xe Xe 4f14 5d4 6s2 Rhenium Re 75 Xe Xe 4f14 5d5 6s2 Osmium Os 76 Xe Xe 4f14 5d6 6s2 Iridium Ir 77 Xe Xe 4f14 5d7 6s2 Platinum Pt 78 Xe Xe 4f14 5d8 6s1 Gold Au 79 Xe Xe 4f14 5d9 6s1 Mercury Hg 80 Xe Xe 4f14 5d10 6s2 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.
Element Symbol At. No. Electronic configuration Actinium Ac 89 Rn Rn 6d1 7s2 Rutherfordium Rf 104 Rn Rn 5f14 6d2 7s2 Hahnium Ha 105 Rn Rn 5f14 6d3 7s2 Seaborgium Sg 106 Rn Rn 5f14 6d4 7s2 Bohrium Bh 107 Rn Rn 5f14 6d5 7s2 Hassium Hs 108 Rn Rn 5f14 6d6 7s2 Meitnerium Mt 109 Rn Rn 5f14 6d7 7s2 Ununnilium (Darmstadtium) Uun 110 Rn Rn 5f14 6d8 7s2 Unununium (Rontgenium) Uuu 111 Rn Rn 5f14 6d10 7s1 Ununbium Uub 112 Rn Rn 5f14 6d10 7s1 Variable Oxidation State of D-block ElementsThe 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. JEE Main Chemistry Chapter-wise Solutions 2023-24JEE Main Chemistry Chapter-wise Solutions 1 Some Basic Concepts in Chemistry 15 P – Block Elements 2 States of Matter 16 D – and F – Block Elements 3 Atomic Structure 17 Co-ordination Compounds 4 Chemical Bonding and Molecular Structure 18 Environmental Chemistry 5 Chemical Thermodynamics 19 Purification and Characterisation of Organic Compounds 6 Solutions 20 General Organic Chemistry 7 Equilibrium 21 Hydrocarbons 8 Redox Reactions and Electrochemistry 22 Organic Compounds Containing Halogens 9 Chemical Kinetics 23 Organic Compounds Containing Oxygen 10 Surface Chemistry 24 Organic Compounds Containing Nitrogen 11 Classification Elements Periodicity Properties 25 Polymers 12 General Principles and Processes of Isolation of Metals 26 Biomolecules 13 Hydrogen 27 Chemistry in Everyday Life 14 S – Block Elements 28 Principles Related to Practical Chemistry Important Related Links for JEE Main 2023-24 JEE Main Study Materials JEE Main 2023 Study Material JEE Main Previous Year Question Papers JEE Main 2023 Revision Notes JEE Main Syllabus 2023 JEE Main Important Questions |
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