1d1 Isotope Relative Abundance

Four isotopes of lead include lead-204, lead-206, lead-207, and lead-208.  The average atomic mass of lead is 207.2.  Which isotope of lead is likely to be the most abundant.

• 204
• 206
• 207
• 208

The atomic mass of an element is the ___.

• average of the mass number and the atomic number for the element

• weighted average of the masses of the isotopes of the element

• total mass of the isotopes of the element

• total number of subatomic particles in the nucleus

Chlorine has two naturally occurring isotopes, Cl-35 and Cl-37, The atomic mass of chlorine is 35.45. Which of these two isotopes of chlorine is more abundant?

• Cl-35

• Cl-37

• Cannot be determined from the information provided.

An isotope has three forms.  10% have a mass of 4 amu, 20% have a mass of 5 amu and 70% have a mass of 6 amu.  

Based on the percentage of abundances above, the average atomic mass will be closest to...

• 3 amu

• 4 amu

• 5 amu

• 6 amu

• None of the above