Answer:
Explanation:
Given that:
The Half-life of 
= 
is less than that of 
Although we are not given any value about the present weight of .
So, consider the present weight in the percentage of to be y%
Then, the time elapsed to get the present weight of = 
Therefore;
here;
= Number of radioactive atoms relating to the weight of y of
Thus:
--- (1)
However, Suppose the time elapsed from the initial stage to arrive at the weight of the percentage of to be = 
Then:
---- (2)
here;
= Number of radioactive atoms of relating to 3.0 a/o weight
Now, equating equation (1) and (2) together, we have:
replacing the half-life of =
( since 
)
∴
The time elapsed signifies how long the isotopic abundance of 235U equal to 3.0 a/o
Thus, The time elapsed is
Mabye yurrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
All the elements in one group have the same number of valence electrons.
In the past a scientist named dalton produced an atomic theory. There were certain problems regarding his views. So, later on scientists like chadwick, rutherford and thompson added some fresh light for the real identification of the atom.
dalton said the atom was the smallest unit and it CANNOT BE DIVIDED ANY FURTHER.
NOTE... this was renected with the discovery of the proton, neutron and electron as the sub atomic particles.
