Q1. Calculate the average atomic mass for Hypothetical Element X using the data provided.

Background

Topic: Average Atomic Mass

This question tests your ability to calculate the average atomic mass of an element using the masses and percent abundances of its naturally occurring isotopes. This is a fundamental concept in atomic structure and is essential for understanding the periodic table.

Key Terms and Formulas

• Isotope: Atoms of the same element with different numbers of neutrons (and thus different masses).

• Average Atomic Mass: The weighted average of the masses of all naturally occurring isotopes of an element.

Formula:

Where fractional abundance is the percent abundance divided by 100.

Step-by-Step Guidance

1. Convert each percent abundance to a decimal (fractional abundance) by dividing by 100.

2. Multiply each isotope's mass by its fractional abundance.

3. Add together all the products from step 2 to set up the sum for the average atomic mass.

4. Write out the full expression for the average atomic mass using the values from the table.

Try solving on your own before revealing the answer!

Q2. For Hypothetical Element Y, determine the percent abundance of each isotope given the average atomic mass and the isotopic masses.

Background

Topic: Isotopic Abundance Calculation

This question tests your ability to use the average atomic mass and the masses of two isotopes to calculate their percent abundances. This is a common problem in atomic structure and helps you understand how the average atomic mass reflects the natural occurrence of isotopes.

Key Terms and Formulas

• Isotopic Abundance: The relative amount of each isotope in a naturally occurring sample of an element.

• Average Atomic Mass Formula (for two isotopes):

Let be the fractional abundance of isotope 1, and for isotope 2.

Step-by-Step Guidance

1. Let represent the fractional abundance of the first isotope (235.04 amu), and for the second isotope (238.05 amu).

2. Set up the equation using the average atomic mass formula:

3. Expand the equation and collect like terms to isolate .

4. Rearrange the equation to solve for (the fractional abundance of the first isotope).

Try solving on your own before revealing the answer!