Question

In the sixth period, the orbitals that are filled are:

• A. $6\mathrm{s},5\mathrm{d},5\mathrm{f},6\mathrm{p}$
• B. $6\mathrm{s},4\mathrm{f},5\mathrm{d},6\mathrm{p}$
• C. $6\mathrm{s},6\mathrm{p},6\mathrm{d},6\mathrm{f}$
• D. $6\mathrm{s},5\mathrm{f},6\mathrm{d},6\mathrm{p}$

Answer 1

The correct option is B

$6\mathrm{s},4\mathrm{f},5\mathrm{d},6\mathrm{p}$

Explanation for the correct option:

Orbitals are filled according to Aufbau's principle.

1. According to Aufbau's principle, the orbital with a lower energy level will be filled first.
2. Order of filing of orbitals: $1\mathrm{s},2\mathrm{s},2\mathrm{p},3\mathrm{s},3\mathrm{p},4\mathrm{s},3\mathrm{d},4\mathrm{p},5\mathrm{s},4\mathrm{d},5\mathrm{p},6\mathrm{s},4\mathrm{f},5\mathrm{d},6\mathrm{p},7\mathrm{s},5\mathrm{f},6\mathrm{d},7\mathrm{p}$.
3. Thus, according to the orbital model first shell has a maximum of 2 electrons.
4. The second and third shells have a maximum of 8 electrons.
5. The fourth and fifth shells have a maximum of 16 electrons and the sixth shell has a maximum of 32 electrons.
6. By starting filling from the first shell according to Aufbau's principle, the sixth shell contain $6\mathrm{s},4\mathrm{f},5\mathrm{d},6\mathrm{p}$ orbits for filling.
7. By following Aufbau's principle option B is correct.

So, the correct answer is Option B.