Atomic Mass and Isotopes

Atomic Mass and Isotopes

by William Lovering

Fill in the Blanks

A nitrogen atom has

protons.

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

A potassium (K) atom is determined to have a mass of 39 AMU. This means it has

neutrons. (number)

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