Understanding Isotopes

Understanding Isotopes

OBJECTIVES

To define and explain isotopes

To calculate the number of neutrons in isotopes of elements

To understand and calculate average atomic mass

ISOTOPE EXAMPLES

Here are three examples of elements and their isotopes. The pink plus represents protons and the green circle represents the neutrons. Notice that the number of protons doesn't change among the isotopes for an element.

Multiple Choice

•Given a nuclear symbol, what does the top left number represent?

• Mass Number

• Atomic Number

• Protons

• Neutrons

Multiple Choice

•Given a nuclear symbol, what does the bottom left number represent?

• Mass Number

• Atomic Number

• Protons

• Neutrons

Multiple Choice

What does the number after the hyphen represent in Li-7?

• Protons

• Neutrons

• Mass Number

• Atomic Number

Multiple Choice

•Boron consists of two isotopes, ¹⁰₅B and ¹¹₅B, what accounts for the difference in the numbers after the hyphen?

• B-10 has 5 protons while B-11 has 6 protons

• B-10 has 10 protons while B-11 has 11 protons

• B-10 has 5 neutrons while B-11 has 6 neutrons

• B-10 has 10 neutrons while B-11 has 11 neutrons

Multiple Choice

How many neutrons does ²⁵₁₂Mg have?

• 12

• 25

• 13

• 37

Multiple Choice

The average atomic mass is based on the mass of all the __________ of the element.

• Atoms

• Neutrons

• Protons

• Isotopes

Multiple Choice

To calculate the average atomic mass you must first multiple what two numbers?

• Atomic number and percent abundance

• Mass number and percent abundance

• Atomic mass and mass number

• Percent abundance by protons

Multiple Choice

Nitrogen-14 has a percent abundance of 99.636% and Nitrogen-15 has a percent abundance of 0.364%. What is the average amount mass for Nitrogen.

• 13.94904

• 0.0546

• 14.003

• 15