For the following calculations SHOW ALL WORK!! (6 points each) 7. The half- life of molybdenum-99 is 67.0 hours. How much of a 1.000 gram sample
remains after 335 hours.

8. Determine the average atomic mass of gallium if 60.00% of its atoms have a mass of
68.926 amu and 40.00% have a mass of 70.925 amu.

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.