Chapter 5

Subatomic Particles, Isotopes, and Nuclear Chemistry

Naturally Occuring Isotopes

Eg. Problem

• Three isotopes exist for argon, element 18• Isotope A: 35.967 amu, %abundance = 0.337• Isotope B: 37.963 amu, % abundance = 0.063• Isotope C: 39.962 amu

• A. What are the mass numbers for the 3 argon isotopes?

• B. What is the percent abundance for the 3rd?

Isobars

• Isobars are atoms that have the same mass number but different atomic numbers.

• Eg.: Iron – 58, and Nickel -58

Challenge Problem

• The principal naturally occuring isotope of Magnesium makes up 78.99% of all Mg atoms and has an atomic mass of 23.98504 u. The other two naturally ocurring isotopes have atomic masses of 24.98584u and 25.98259 u, respectively. What are the percent abundances of these other two isotopes of magnesium?

Small Group Problem

• Above each square inch of the Earth’s surface is 14.7 lbs of air. The density of air at sea level is about 1.27 g/L. The Earth is 7930 miles in diameter and has a mass of 5.98 x 1024kg

• A) use the above data, as needed, to determine the mass in kilograms of the Earths atomosphere.

• B) Determine the average density of Earth in grams per milliliter.

• Glass microballoons are hollow spheres, averaging about 0.070 mm in diameter, used as filler for certain types of lightweight composite material. A 1.00 L package of microballoons has a mass of only about 62 g, even though the microballoons occupy 68% of the total volume available when packed tightly.

• A) If the glass itself has a density of 2.2 g/cm3 about how thick is the glass in the average microballoon?

• B) A composite material is made by filling the psace between microballoons with epoxy glue( density = 1.67 g/mL) . Calculate the density of this composite mixture.

• The relative abundances of hydrogen-1 (protium) and hyrdogen-2 (deuterium) are 99.99% and 0.01% respectively. Write the formulas for the different types of hydrogen molecules found in nature. Which type would be most abundant, and which would be least abundant? If a container held one billion molecules of Hydrogen, about how many of them would be of the least abundant type?