Two radioactive nuclides decay by successive first-order processes: (the quantities over the arrows are the half-lives in days). suppose that y is an isotope that is required for medical applications. at what time after x is first formed will y be most abundant?

Hi your question was incomplete because the two half lives were not given, hence I have attached the full version of the question in the  attachment below.

38.9 Days

Explanation:

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.