Advertisements
Advertisements
प्रश्न
How would you account for the irregular variation of ionization enthalpies (first and second) in the first series of the transition elements?
Advertisements
उत्तर १
Ionization enthalpies are found to increase in the given series due to a continuous filling of the inner d-orbitals. The irregular variations of ionization enthalpies can be attributed to the extra stability of configurations such as d0, d5 and d10. Since these states are exceptionally stable, their ionization enthalpies are very high.
In terms of first ionization energy, Cr has low ionization energy. This is because after losing one electron, it attains the stable configuration (3d5). On the other hand, Zn has exceptionally high first ionization energy, as an electron has to be removed from stable and fully-filled orbitals (3d10 4s2).
The second ionization energies are higher than the first since it becomes difficult to remove an electron when an electron has already been removed. Also, elements like Cr and Cu have exceptionally high second ionization energies, as after losing the first electron, they have attained the stable configuration (Cr+: 3d5 and Cu+: 3d10). Hence, taking out one electron more from this stable configuration will require a lot of energy.
उत्तर २
The irregular variations in ionization enthalpy are due to differences in the stability of different 3d configurations (e.g., d0, d5, d10 are unusually stable).
APPEARS IN
संबंधित प्रश्न
Give reasons:
Transition metals show variable oxidation states.
Account for the following:
Cu+ ion is unstable in aqueous solution.
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?
Which is a stronger reducing agent, Cr2+ or Fe2+ and why?
Why do transition metals exhibit higher enthalpy of atomization?
Give reasons for the following:
The transition metals generally form coloured compounds.
Maximum magnetic moment is shown by ____________.
Maximum oxidation state is shown by ____________.
Metallic radii of some transition elements are given below. Which of these elements will have highest density?
| Element | \[\ce{Fe}\] | \[\ce{Co}\] | \[\ce{Ni}\] | \[\ce{Cu}\] |
| Metallic radii/pm | 126 | 125 | 125 | 128 |
The magnetic nature of elements depends on the presence of unpaired electrons. Identify the configuration of transition element, which shows highest magnetic moment.
\[\ce{KMnO4}\] acts as an oxidising agent in acidic medium. The number of moles of \[\ce{KMnO4}\] that will be needed to react with one mole of sulphide ions in acidic solution is ______.
Transition elements show high melting points. Why?
Assertion: \[\ce{Cu^2+}\] iodide is not known.
Reason: \[\ce{Cu^2+}\] oxidises \[\ce{I^-}\] to iodine.
Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.
Read the passage given below and answer the following question.
|
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. |
Researchers have uncovered the youngest known dinosaur bone, dating around 65 million years ago. How was the age of this fossil estimated?
Catalytic hydrogenation of benzene gives
Which of the following species has maximum magnetic momentum?
Why is the `"E"_(("V"^(3+)//"V"^(2+)))^"o"` value for vanadium comparatively low?
Write the ionic equation for reaction of KI with acidified KMnO4.
