The molar mass of sucrose is measured to be 342.3 g. the value of avogadro's number, correct to six significant digits, is 6.022 14 x 1023. the number of molecules in 0.24g of sucrose, written with an appropriate number of significant digits is
a) 4.2 x 1020
b) 4.22 x 1020
c) 4.222 x 1020
d) 4.222 4 x 1020

im almost positive the answer is A.) 4.2 x 1020, im very sorry if im mistaken.

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.