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The d-And-f-Block Elements

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Chemistry I

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Chemistry

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How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?


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, d10. Since these states are exceptionally stable, their ionization enthalpies are very high.

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Silver atom has a completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?


Ag has a completely filled 4d orbital (4d10 5s1) in its ground state. Now, silver displays two oxidation states (+1 and +2). In the +1 oxidation state, an electron is removed from the s-orbital. However, in the +2 oxidation state, an electron is removed from the d-orbital. Thus, the d-orbital now becomes incomplete (4d9). Hence, it is a transition element. wherein it will have incompletely filled d-orbitals (4d), hence a transition metal.
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Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Both oxide and fluoride ions are highly electronegative and have a very small size. Due to these properties, they are able to oxidize the metal to its highest oxidation state.

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The E° (M2+/M) value for copper is positive (+ 0.34 V). What is possibility the reason for this? 

Copper has high atomisation ΔaH° and low hydration energy  Δhyd H°. Due to which the E° value is positive.
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In the series Sc (Z = 21) to Zn(Z = 30), the enthalpy of atomisation of zinc is the lowest i.e., 26, kJ mol. Why?

The extent of metallic bonding an element undergoes deideds the enthalpy of atomization the more extensive the metallic bonding of an element the more will be its enthalpy of atomization.

Sc & Zn belongs to 3
rd group of periodic table. In all transition metals (except Zn, electronic configuration: 3d10 4s2), there are some unpaired electrons that account for their stronger metallic bonding. Due to the absence of these unpaired electrons, the inter-atomic electronic bonding is the weakest in Zn and as a result, it has the least enthalpy of atomization.
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