Hello!
The half-life is the time of half-disintegration, it is the time in which half of the atoms of an isotope disintegrate.
We have the following data:
mo (initial mass) = 20 g
m (final mass after time T) = 5 g
x (number of periods elapsed) = ?
P (Half-life) = ? (in minutes)
T (Elapsed time for sample reduction) = 8 minutes
Let's find the number of periods elapsed (x), let us see:






Now, let's find the half-life (P) of the radioactive sample, let's see:





I Hope this helps, greetings ... DexteR! =)
It is called a dactyloscopy
Answer:
The elements that are commonly positive ions are metals. But there are a few gases that can become positively charged by losing electrons.
Answer: Lanthanide and actinide series
Explanation: The elements with partially or fully filled f orbitals belong to f block elements.
f block elements include lanthanides and actinides. They are called so the lanthanides contain the first element named as lanthanum and actinides contain first element named as actinium. They are also called as inner transition elements.
All of them have general electronic configuration:
, where n = 6-7
Chemical change because it cannot be reversed