Achemist finds that 30.82g of nitrogen will react with 17.60g , 35.20g, or 88.00g of oxygen to form four different compounds. calculate the mass of oxygen per gram of nitrogen for each compound.

17.60 g / 30.82 = 0.57  

35.20g / 30.82 = 1.14 (twice as much oxygen as the first)  

70.40 / 30.82 = 2.28 (4 X's as much oxygen as the first)  

88.00 / 30.82 = 2.85 (5 X's as much oxygen as the first)  

"the law of multiple proportions to the idea that chemical combination consists in the interaction of atoms of definite and characteristic weight"

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.