JEE Main20203 Sep 2020Evening ShiftChemistryStructure of AtomActual
Consider the hypothetical situation where the azimuthal quantum number, l , takes values 0 , 1 , 2 , … … . . n + 1 . Where n is the principal quantum number. Then, the element with atomic number:
Options
- A9 is the first alkali metal
- B13 has a half-filled valence subshell
- C8 is the first noble gas
- D6 has a 2p-valence subshell
Correct answer
B. 13 has a half-filled valence subshell
Step-by-step solution
For n = 1 value of l = 0 ,   1 ,   2 For n = 2 value of l = 0 ,   1 ,   2 ,   3 So, according to n + l rule the filling order of subshells will be : 1 s   1 p   2 s   1 d   2 p   3 s   2 d   3 p   4 s . . . . . (1) 1 st alkali metal will have configuration 1 s 2   1 p 6 so atomic number will be 8 . (2) 1 st alkali metal will have electronic configuration ⇒       1 s 1       ⇒     Z = 1 (3) Elect