U-238 which has a long half-life is also find the ages of geological formations (rocks). Meanwhile I-131, which has much shorter half-life, is used for diagnosing thyroid disorders. What is the mass of an original 5.6 gram sample of I-131 that is still radioactive after 16.042 days?

The mass after 16.042 days : 1.4 g

Given

mass of 5.6 gram sample of I-131

time=16.042 days

Required

The mass of a sample

Solution

General formulas used in decay:  

T = duration of decay  

t 1/2 = half-life  

N₀ = the number of initial radioactive atoms  

Nt = the number of radioactive atoms left after decaying during T time  

Half-life of I-131 = 8 days

Input the value :

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

i do not get it   at all