Barium reacts with water to produce barium hydroxide and hydrogen gas. How many moles of barium hydroxide are produced when 250.0 mL of water is consumed? What is the total number of moles of ions from barium hydroxide produced in this reaction?

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.  

it is the most commonly accepted one