If Aufbau rule is not obeyed and the electronic filling occurs orbit by orbit till saturation is reached (for a given principal quantum number $n$ , electrons are filled in the increasing order of azimuthal quantum number $l$ ), then the percentage change in sum of all $(n + l)$ values for unpaired electrons in an atom of iron is $10 x$ . What is the value of $x$ ?

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Answer 1

When $n + l$ rule is obeyed, the configuration is

$^{26} F e = 1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 4 s^{2}, 3 d^{6} .$

Since, $(n + l)$ for each unpaired electron is $5$ , so for $4$ unpaired electrons in $^{26} F e$ , $(n + l)$ is $5 \times 4 = 20$ .

When $n + l$ rule is not obeyed, the configuration is

$^{26} F e = 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{8} .$

Since, $(n + l)$ for each unpaired electron is $5$ , so for $2$ unpaired electrons in $^{26} F e$ , $(n + l)$ is $5 \times 2 = 10$ .

Now,
% change $= \frac{2 0 - 1 0}{2 0} \times 100 = 50 = 10 x$ .

$∴ x = 5 .$

Answer 2

When

n + l

rule is obeyed, the configuration is

^{26} F e = 1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 4 s^{2}, 3 d^{6} .

Since,

(n + l)

for each unpaired electron is

5

, so for

4

unpaired electrons in

^{26} F e

,

(n + l)

is

5 \times 4 = 20

.

When

n + l

rule is not obeyed, the configuration is

^{26} F e = 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{8} .

Since,

(n + l)

for each unpaired electron is

5

, so for

2

unpaired electrons in

^{26} F e

,

(n + l)

is

5 \times 2 = 10

.

Now,
% change

= \frac{2 0 - 1 0}{2 0} \times 100 = 50 = 10 x

.

∴ x = 5 .

$5$

$6$

$7$

$3$

Angular momentum in an orbit is $3 n$ . The value of $n$ is :

For a particular principal quantum number, the energy will be maximum for the orbital:

The maximum number of electrons that can have principal quantum number, $n = 3$ , and spin quantum number, $m_{s} = - 1 / 2$ , is:

The statement "No two electrons in an atom can have all the four quantum numbers identical" is known as:

The maximum number of electrons that can have principal quantum number, n=3 and spin quantum number, $s = 1 / 2$ , is _______ .

Revise with Concepts

Electron Configuration

5

6

7

3

Angular momentum in an orbit is 3n. The value of n is :