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Poor shielding of nuclear charge by d or...

Poor shielding of nuclear charge by `d` or `f`-orbital electrons is responsible for which of the following facts?

A

Atomic radius of `Nb(4d`-series) is comparable to that of `Ta(5d`-series)

B

The `1^(st)` ionisation enthalpy of copper is less than that of zinc

C

The value of electron gain enthalpy is more negative for sulphur than for oxygen

D

The `1^(st)` ionisation energy for gold is greater than that of silver.

Text Solution

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The correct Answer is:
A, D
The `d` and `f` orbitals do not shield the nucleus charge very effectively. Therefore there is significant reducion in the size of the ions, just after `d` or `f` orbitals have been filled completely. This is called lanthanide contraction. Atomic radii of `Nb (Nb^(3+) = 0.72 Å)` and `Ta(Ta^(3+) = 0.72 Å)` are almost identical due to lanthanide contraction. This is also the reason for the higher ionisation energy of gold than silver.
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Poor shielding of nuclear charge by d or f-orbital elements is responsible for which of the following facts?

Nuclear charge actually experienced by an electron is termed as effective nuclear charge The effective nuclear Z^(**) actually depends on type of shell and orbital in which electron is actually present. The relative extent to which the various orbitals penetrate is . s gt p gt d gt f (for the same value of n) The phenomenon in which penulitmate shell electrons act as screen or shield in between nucleus adn valence shell electrons and there by reducing nuclear charge is known as sheilding effect. The penultimate shell electrons repel the valence shell electron to keep them loosely held with nucleus . It is thus evident that more is the shielding effect, lesser is the effective nuclear charge and lesser is the ionizatio energy. In which of the following valence electron experience maximum effective nuclear charge?

Nuclear charge actually experienced by an electron is termed as effective nuclear charge. The effective nuclear charge Z^(**) actuall ydepends on type of shell and orbital in which electron is actually present. The relative extent to which the various orbitals penetrate the electron clouds of other orbitals is s gt p gt d gt f (for the same value of n) The phenomenon in which penultimate shell electrons act as screen or sheild in between nucleus and valence shell electrons and thereby reducing nuclear charge is known as shielding effect. the penultimate shell electrons repel the valence shell electron to keep them loosely held with nucleus. it is thus evident that more is the shielding effect, lesser is the effective nuclear charge and lesser is the ionization energy. Q. Which of the following valence electron experience maximum effective nuclear charge?

Nuclear charge actually experienced by an electron is termed as effective nuclear charge The effective nuclear Z^(**) actually depends on type of shell and orbital in which electron is actually present. The relative extent to which the various orbitals penetrate is . s gt p gt d gt f (for the same value of n) The phenomenon in which penulitmate shell electrons act as screen or shield in between nucleus adn valence shell electrons and there by reducing nuclear charge is known as sheilding effect. The penultimate shell electrons repel the valence shell electron to keep them loosely held with nucleus . It is thus evident that more is the shielding effect, lesser is the effective nuclear charge and lesser is the ionizatio energy. Which of the following is not concerned to effective nuclear charge?

" The effective nuclear charge of Nitrogen for 2p electron (last electron) is "

J.C. Slater proposed an empirical constant that represents the cumulative extent to which the other electrons of an atom shield (or screen) any particular electron from the nuclear charge. Thus, slater's screening contant sigma is as : Z^(**)=Z-sigma Here, Z is the atomic number of the atom, and hence is equal to the actual number of protons in the atom. the parameter Z^(**) is the effective nuclear charge, which according to is smaller than Z, since the electron in question is screened (shielded) from Z by an amount sigma . Conversely, an electron that is well shielded from the nuclear charge Z experiences a small effective nuclear charge Z^(**) . The value of sigma for any one electron in a given electron configuration (i.e., in the presence of the other electrons of the atom in question) is calculated using a set of empirical rules developed by slater. according to these rules, the value of sigma for the electron in question is the cumulative total provided by the various other electrons of the atom. Q. Which of the following statement is correct?

The effective nuclear charge on the added electron in F-atom , in the formation of negative ion is

RESONANCE-PERIODIC TABLE & PERIODICITY-Advanced Level Problems
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  2. Which of the following statement is wrong for the d-block elements?

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  15. EA(1) value of some group of p-Block elements ae given: a, b, c……...

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