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प्रश्न
What are the characteristics of the transition elements and why are they called transition elements?
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उत्तर
The general characteristics of transition elements are as follows:
- Electronic configuration: General electronic configuration is (n − 1) d1−10ns0−2. This configuration reflects the filling of d-orbitals in addition to the s-orbitals of the outermost shell.
- Metallic character: Transition elements, except for Zn, Cd and Hg, exhibit metallic structures and typical metallic properties like malleability, ductility and conductivity.
- Atomic and ionic size: Across a transition series, the atomic and ionic radii decrease due to the increasing nuclear charge, which pulls the d-electrons closer to the nucleus (a phenomenon called the lanthanide contraction).
- Oxidation state: They exhibit variable oxidation states due to the participation of both d and s-electrons in bonding. Common oxidation states range from +2 to +7, depending on the element.
- Paramagnetism: Ions with unpaired d-electrons exhibit paramagnetism. The greater the number of unpaired electrons, the stronger the paramagnetic behavior.
- Ionisation enthalpy: Ionization enthalpy increases gradually across the series due to the increasing nuclear charge, making it harder to remove electrons.
- Formation of coloured ions: Transition metal ions are often colored because of electronic transitions within the d-orbitals (specifically d-d transitions) when they absorb visible light.
- Formation of complex compounds: Transition metals form complexes due to their small size, high charge density, and availability of vacant d-orbitals to accept electron pairs from ligands.
- They possess catalytic properties: They act as catalysts due to their ability to exist in multiple oxidation states, which facilitates various chemical reactions.
- Formation of interstitial compounds: Transition metals can form interstitial compounds by trapping small non-metal atoms (like H, C, N) in their crystal lattice.
- Alloy formation: They easily form alloys due to similar atomic sizes, which allows different metal atoms to substitute one another in the crystal structure.
They are positioned between s and p-block elements and are known as transition elements because of their incompletely filled d-orbitals in the ground state or any stable oxidation state.
संबंधित प्रश्न
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Answer the following question:
Which element of the first transition series has lowest enthalpy of atomisation?
On the basis of the figure given below, answer the following questions:
- Why Manganese has lower melting point than Chromium?
- Why do transition metals of 3d series have lower melting points as compared to 4d series?
- In the third transition series, identify and name the metal with the highest melting point.
Read the passage given below and answer the following question.
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Are there nuclear reactions going on in our bodies? There are nuclear reactions constantly occurring in our bodies, but there are very few of them compared to the chemical reactions, and they do not affect our bodies much. All of the physical processes that take place to keep a human body running are chemical processes. Nuclear reactions can lead to chemical damage, which the body may notice and try to fix. The nuclear reaction occurring in our bodies is radioactive decay. This is the change of a less stable nucleus to a more stable nucleus. Every atom has either a stable nucleus or an unstable nucleus, depending on how big it is and on the ratio of protons to neutrons. The ratio of neutrons to protons in a stable nucleus is thus around 1 : 1 for small nuclei (Z < 20). Nuclei with too many neutrons, too few neutrons, or that are simply too big are unstable. They eventually transform to a stable form through radioactive decay. Wherever there are atoms with unstable nuclei (radioactive atoms), there are nuclear reactions occurring naturally. The interesting thing is that there are small amounts of radioactive atoms everywhere: in your chair, in the ground, in the food you eat, and yes, in your body. The most common natural radioactive isotopes in humans are carbon-14 and potassium-40. Chemically, these isotopes behave exactly like stable carbon and potassium. For this reason, the body uses carbon-14 and potassium-40 just like it does normal carbon and potassium; building them into the different parts of the cells, without knowing that they are radioactive. In time, carbon-14 atoms decay to stable nitrogen atoms and potassium-40 atoms decay to stable calcium atoms. Chemicals in the body that relied on having a carbon-14 atom or potassium-40 atom in a certain spot will suddenly have a nitrogen or calcium atom. Such a change damages the chemical. Normally, such changes are so rare, that the body can repair the damage or filter away the damaged chemicals. The natural occurrence of carbon-14 decay in the body is the core principle behind carbon dating. As long as a person is alive and still eating, every carbon-14 atom that decays into a nitrogen atom is replaced on average with a new carbon-14 atom. But once a person dies, he stops replacing the decaying carbon-14 atoms. Slowly the carbon-14 atoms decay to nitrogen without being replaced, so that there is less and less carbon-14 in a dead body. The rate at which carbon-14 decays is constant and follows first order kinetics. It has a half-life of nearly 6000 years, so by measuring the relative amount of carbon-14 in a bone, archeologists can calculate when the person died. All living organisms consume carbon, so carbon dating can be used to date any living organism, and any object made from a living organism. Bones, wood, leather, and even paper can be accurately dated, as long as they first existed within the last 60,000 years. This is all because of the fact that nuclear reactions naturally occur in living organisms. |
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\[\ce{Sn^{2+}_{ (aq)} + 2e^- -> Sn_{(s)}}\]; E0 = −0.14 V
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A pair of coloured ions is ______.
Account for the following:
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