The famous scientist Louis Pasteur incorrectly assumed that the process of fermentation was a biological process, not one that was possible using ordinary chemistry. Of course, he was mistaken. One form of protein bridged the biological/chemical divide, allowing processes to take place both within and outside of cells. What are these proteins called, and how do they allow Pasteur to do what he thought was impossible?

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.