# (solved)Question 2.63 of NCERT Class XI Chemistry Chapter 2

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 ?

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### Question 2.63NCERT 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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