Due to inter electronic repulsion, an electron experiences less nuclear charge. It is, therefore, said that inner electronic shells electrons shield the nucleus. The actual nuclear charge experienced by an electron is called effective nuclear charge. If the electrons in K-shell shields the nucleus to the extent of 0.5 (say) each. What will be the wave number of the spectral line arising out of n=4 to n = 2 transition in He atom?

\frac{3}{4} R_{H}

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\frac{3}{8} R_{H}

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\frac{R_{H}}{4}

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8 R_{H}

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Solution

The correct option is B $\frac{3}{4} R_{H}$
As we know,
$¯ v = R_{H} \times Z^{2} (\frac{1}{n_{1}^{2}} - \frac{1}{n_{2}^{2}})$ , where $R_{H}$ is a Rydberg's constant $(R = 1.1 \times 10^{7} m^{- 1})$
so here,
$¯ v = R_{H} \times 2^{2} (\frac{1}{2^{2}} - \frac{1}{4^{2}}) = R_{H} \times (3 / 4)$

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Similar questions

Q. The nuclear charge actually experienced by an electron is termed as the effective nuclear charge. The effective nuclear charge Z* actually depends on the 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 > p > d > f

(for the same value of

n

)
The phenomenon in which penultimate shell electrons act as screen or shield 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 the nucleus. It is thus evident that more is the shielding effect, lesser is the effective nuclear charge and lesser is the ionization energy.
Which of the following valence electron experience maximum effective nuclear charge?

The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus?

Q. Arrange

s, p

and

d

sub-shells of a shell in the increasing order to effective nuclear charge

(Z_{e f f})

experienced by the electron present in them.

The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electrons in 4p orbital. Which of these electron experiences the lowest effective nuclear charge?

Q. The unpaired electrons in Al and Si are present in 3p orbital. In which element (Al or Si), electrons will experience more effective nuclear charge from the nucleus?

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The correct option is B 34RHAs we know,¯v=RH×Z2(1n21−1n22), where RH is a Rydberg's constant (R=1.1×107m−1)so here,¯v=RH×22(122−142)=RH×(3/4)

The correct option is B $\frac{3}{4} R_{H}$
As we know,
$¯ v = R_{H} \times Z^{2} (\frac{1}{n_{1}^{2}} - \frac{1}{n_{2}^{2}})$ , where $R_{H}$ is a Rydberg's constant $(R = 1.1 \times 10^{7} m^{- 1})$
so here,
$¯ v = R_{H} \times 2^{2} (\frac{1}{2^{2}} - \frac{1}{4^{2}}) = R_{H} \times (3 / 4)$