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प्रश्न
Give reasons:
Transition metals show variable oxidation states.
Account for the following:
Transition metals show variable oxidation states.
Explain giving reasons:
Transition elements exhibit variable oxidation states.
Why do transition elements exhibit variable oxidation states?
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उत्तर १
- The variable oxidation states of transition elements are due to the participation of ns and (n − 1) d-electrons in bonding.
- A lower oxidation state is exhibited when the ns-electrons take part in bonding.
- Higher oxidation states are exhibited when the (n − 1) d-electrons take part in bonding.
- Since there is very little energy difference between these orbitals, both energy levels can be used for bond formation.
Thus, transition elements exhibit variable oxidation states.
उत्तर २
- In transition elements, the 3d and 4s electrons are close in energy and can be lost in different numbers during reactions.
- The involvement of both (n − 1) d and ns electrons in bonding allows multiple oxidation states.
- Stability of oxidation states is influenced by half-filled or fully filled d-subshells, leading to preferred oxidation numbers.
- For example, manganese shows oxidation states from +2 to +7, reflecting this variability.
Hence, transition elements show a wide range of oxidation states because they can lose different numbers of d and s electrons easily.
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संबंधित प्रश्न
To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with examples.
Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why?
Why do transition metal ions possess a great tendency to form complexes?
Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?
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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Zn, Cd, and Hg are soft metals.
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Oxidation states
