Question

What is the equation for the fraction of atoms? Explain all parts.

Answer 1

I'm sorry, I don't know what you mean. Could you rephrase the question, or give some background into what you're trying to do?

Answer 2

this is the whole question. i) explain half life in your own words.
ii) What is the equation for the fraction of atoms? Explain all parts.
iii) Why is half life useful? Explain at least 2 reasons

Answer 3

Okay, that is more helpful. By "the equation for the fraction of atoms", you mean the fraction of radioactive atoms that remain after some time t. That is the following:
\[\frac{N}{N_0} = e^{-\lambda t} \]
where
\[ \lambda = \frac{\ln(2)}{t_{1/2}} \]
and
\[t_{1/2}\]
is the half life.