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Assertion : The value of enthaply of ato...

Assertion : The value of enthaply of atomisation is maximum at about the middle of each series.
Reason : There is one uparied electron per d-orbital and this results in stronger interatomic interaction.

A

If both assetion and reason are true and the reason is the correct explanation of the assertion.

B

If both assertion and reason are ture but reason is not the correct explanation of the assertion.

C

If assertion is true but reason is false.

D

If assertion is false but reason is true.

Text Solution

Verified by Experts

The correct Answer is:
A
Greater the numbe of valence electrons, stronger is the resultant bonding and higher the enthalpy of atomisation.
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Read the given passage and answer the questions number 1 to 5 that follow : In general, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number. This is because the new electron enters a d-orbitals each time the nuclear charge increases by unity. It may be recalled that the shielding effect of a d-electron is not that effective, hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases. The same trend is observed in the atomic radii of a given series. However, the variation within a series is quite small. An interesting point emerges when atomic sizes of one series are compared with those of the corresponding elements in the other series. We find an increase from the first (3d) to the second (d) series of the elements but the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbitals results in a regular decrease in atomic radii called Lanthanoid contraction. Compare the shielding effect of s, p, d and f-orbitals.

Read the given passage and answer the questions number 1 to 5 that follow : In general, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number. This is because the new electron enters a d-orbitals each time the nuclear charge increases by unity. It may be recalled that the shielding effect of a d-electron is not that effective, hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases. The same trend is observed in the atomic radii of a given series. However, the variation within a series is quite small. An interesting point emerges when atomic sizes of one series are compared with those of the corresponding elements in the other series. We find an increase from the first (3d) to the second (d) series of the elements but the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbitals results in a regular decrease in atomic radii called Lanthanoid contraction. What is lanthanoid contraction ?

Knowledge Check

  • Assertion: The metals of 4d and 5d greater entalpies of atomisation than the corresponding elements of the 3d series. Reason: The metal-metal bond in 4d and 5d series are stronger than those in the 3d series.

    A
    If both (A) and (R) are correct and (R) is the correct explanation of (A).
    B
    If both (A) and (R) are correct, but (R) is not the correct explanation of (A).
    C
    If (A) is correct, but (R) is incorrect.
    D
    If (A) is incorrect but (R) is correct.

  • Assertion : In transition elements radii of 5d series are virtually the same as those of the corresponding members of 4d series. Reason : The filling of 4f orbitals before 5d orbitals results in regular decrease in atomic radii.

    A
    If both assertion and reason are true and reason is the correct explanation of assertion.
    B
    If both assertion and reason are true and reason not is the correct explanation of assertion.
    C
    If assertion is trun but reason is false.
    D
    If both assertion and reason are false.

  • Read the passage given below and answer the following questions: Within the 3d series, manganese exhibits oxidation states in aqueous solution from +2 to +7, ranging from Mn^(2+)(aq) to MnO_(4)^(-) (aq). Likewise, iron forms both Fe^(2+)(aq) and Fe^(3+)(aq) as well as the FeO_(4)^(2-) ion. Cr and Mn form oxyions CrO_(4)^(2-) , MnO_(4)^(-) , owing to their willingness to form multiple bonds . The pattern with the early transition metals-in the 3d series up to Mn, and for the 4d, 5d metals up to Ru and Os—is that the maximum oxidation state corresponds to the number of ‘‘outer shell’’ electrons. The highest oxidation states of the 3d metals may depend upon complex formation (e.g., the stabilization of Co^(3+) by ammonia) or upon the pH (thus MnO_(4)^(2-) (aq) is prone to disproportionation in acidic solution). Within the 3d series, there is considerable variation in relative stability of oxidation states, sometimes on moving from one metal to a neighbor, thus, for iron, Fe^(3+) is more stable than Fe^(2+) , especially in alkaline conditions, while the reverse is true for cobalt. The ability of transition metals to exhibit a wide range of oxidation states is marked with metals such as vanadium, where the standard potentials can be rather small, making a switch between states relatively easy. (Cotton, S. A. (2011). Lanthanides: Comparison to 3d metals. Encyclopedia of inorganic and Bioinorganic Chemistry.) In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage. Assertion: Highest oxidation state is exhibited by transition metal lying in the middle of the series. Reason: The highest oxidation state exhibited corresponds to number of (n-1)d electrons.

    A
    Assertion and reason both are correct statements and reason is correct explanation for assertion.
    B
    Assertion and reason both are correct statements but reason is not correct explanation for assertion.
    C
    Assertion is correct statement but reason is wrong statement.
    D
    Assertion is wrong statement but reason is correct statement.

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    Read the given passage and answer the questions number 1 to 5 that follow : In general, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number. This is because the new electron enters a d-orbitals each time the nuclear charge increases by unity. It may be recalled that the shielding effect of a d-electron is not that effective, hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases. The same trend is observed in the atomic radii of a given series. However, the variation within a series is quite small. An interesting point emerges when atomic sizes of one series are compared with those of the corresponding elements in the other series. We find an increase from the first (3d) to the second (d) series of the elements but the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbitals results in a regular decrease in atomic radii called Lanthanoid contraction. Name the elements with atomic number 25, 26, 27.

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