Dialysis is often used to change the buffer that protein is in. if a protein is in 50 ml of hepes buffer (7.4) and is dialyzed overnight with 4 liters of imidazole(6.8), how much (%) of hepes buffer has been removed from the protein?

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.