Question 2.63
NCERT Class XI Chemistry
The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electron in 4p orbital. Which of these electron experiences the lowest effective nuclear charge ?
Note: Q 2.57 to 2.62 are simple enough. So they have been skipped. Please write an email to us if you face any difficulty with any of them.Solution (Method 1)
(video solution below this)
First calculate the energies
$\displaystyle n + l \text{ for } 2p = 2 + 1 = 3$
$\displaystyle n + l \text{ for } 3p = 3 + 1 = 4$
$\displaystyle n + l \text{ for } 4p = 4 + 1 = 5$
most probable distance from the nucleus
increases as the energy $\displaystyle n + l$ increases
$\displaystyle \therefore $ lowest penetration is of 4p electrons
less penetration means more shielding
and hence less effective nuclear charge
$\displaystyle \therefore $ 4p electrons experience least $\displaystyle Z_{eff} \:\underline{Ans}$
Video Explanation for Method 1
Please watch this youtube video for a quick explanation of the solution:
Solution (Method 2)
First write the electronic configuration
$\displaystyle 1s^22s^22p^63s^23p^64s^23d^{10}4p^5$
we observe that the $\displaystyle 4p$ electrons are shielded by the most number of electrons, especially the d-electrons which have a greater shielding effect
hence, 4p experience the least $\displaystyle Z_{eff}\:\underline{Ans}$
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