Atomic Mass and Isotopes

Atomic Mass and Isotopes

by William Lovering

Fill in the Blanks

Multiple Choice

An atom has 15 protons, 17 neutrons, and 15 electrons. What is its atomic number?

• 15

• 17

• 32

• 30

Multiple Choice

An atom has 15 protons, 17 neutrons, and 15 electrons. What is its mass?

• 15

• 17

• 32

• 30

Fill in the Blanks

Multiple Choice

$$\ ^{16}O\ and\ ^{18}O$$  

Which of these oxygen isotopes has the most protons?

• $$^{16}O$$  

• $$\ ^{18}O$$  

• They are the same

Multiple Choice

$$\ ^{16}O\ and\ ^{18}O$$  

Which of these oxygen isotopes has the most neutrons?

• $$^{16}O$$  

• $$\ ^{18}O$$  

• They are the same

Multiple Choice

Which boron isotope would have the most stable nucleus?

• B-10

• B-11

• B-5

• B-6

Multiple Choice

Which isotope of sulfur is most likely to be radioactive?

• S-32

• S-33

• S-34

Multiple Choice

If X is the symbol for an element, which of the following two symbols represent    isotopes of the same element?     I. ⁷⁷₃₅X  II. ⁷⁷₃₃X  III. ⁸¹₃₇X  IV. ⁸¹₃₅ X

• I and II

• III and IV

• I and IV

• I and III

Multiple Choice

Rubidium has two common isotopes, ⁸⁵Rb and ⁸⁷Rb. If the abundance of ⁸⁵Rb is 72.2% and the abundance of ⁸⁷Rb is 27.8%, what is the average atomic mass of rubidium?

• 85.468 amu

• 37 amu

• 85.6 amu

• 86.4 amu

Multiple Choice

There are two primary isotopes found in any sample of copper: copper-63 and copper-65. The isotope ⁶⁵Cu composes 69.2% of the sample and ⁶³Cu comprises the other 30.8%. Based on this data, what is the atomic mass of copper?

• 29 amu

• 63.546 amu

• 64.4 amu

• 63.6 amu

Multiple Choice

How many protons does this isotope of titanium have?

• 48

• 22

• 26

• 70

Multiple Choice

Isotopes are atoms of the same element with different #’s of __________ & therefore different __________.

• neutrons ; atomic numbers

• protons ; atomic numbers

• electrons ; mass numbers

• neutrons ; mass number

Multiple Choice

Magnesium exists as the three isotopes shown. What is the average atomic mass of magnesium?

• 20.74 amu

• 22.56 amu

• 18.39 amu

• 24.31

Multiple Choice

To calculate average atomic mass, you need

• the atomic mass of each isotope

• the percent abundance of each isotope

• the atomic mass and percent abundance of each isotope

• to find the average of the atomic masses of each isotope

Multiple Choice

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.

Multiple Choice

Nitrogen has three occurring isotopes: Nitrogen-13, Nitrogen-14, Nitrogen-15. Which isotope is the most abundant?

• Nitrogen-13

• Nitrogen-14

• Nitrogen-15

• Based on the information given, it cannot be determined