(ii) Butane has the formula C4H10.
Calculate the mass of carbon in 100 g of butane.
Give your answer to three significant figures.
(relative atomic masses: H = 1.00, C = 12.0;
relative formula mass: C4H10 = 58.0)
You must show your working.

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.  

i think it's letter a.