below 30th 29

29. a) For the element with atomic number 24 
i) Write the electronic configuration. 
ii)Write the value of 'n' and 'I' for its electron in the value shell. 
iii) How many unpaired electrons are present in it? 
b) State Pauli's exclusion principle. Is it possible to have configuration ls³ ?

30. a) Write any two demerits of Bohr's atomic model. 
b) Name the quantum number that specifies 
i) size of an orbital 
ii) shape of an orbital 
c) Write the equation which gives relation between wav 
($\mathrm{\lambda }$) and momentum (p) of a material particle. 

 

Dear student

29.
a)The element with atomic number 24 is Cr
i)The electronic configuration is [Ar]3d⁵4s¹
​ii) The value of n and l for the electron in the valence shell is n=4, l = {n-1}= 0,1,2,3 
iii)Chromium has 6 unpaired electrons



b)
b)
Pauli’s exclusion principle states that no two electrons in an atom can have the same value of four quantum numbers.Thus, it excludes the electrons from having the same quantum numbers and hence it is called exclusion principle.

The configuration 1s³ is not possible because,each orbital can occupy a maximum of 2 electrons only. So after filling the 1s orbital, as 1s², the next electron occupies  the next orbitals.

Regards