$$\text{Number of neutrons} = \text{Mass number} - \text{Atomic number}$$

$$\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which statement best describes the atomic number of an element?

Accepted Answer

It is the number of protons in the nucleus of an atom.

Question 2

A neutral atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

12

Question 3

If an atom has 19 protons, 19 electrons, and 20 neutrons, what is its mass number?

Accepted Answer

39

Question 4

Which of the following atoms is electrically neutral?

Accepted Answer

An atom with 8 protons and 8 electrons

Question 5

A lead (Pb) atom has a mass number of 207 and an atomic number of 82. How many neutrons are present in this atom?

Accepted Answer

125

Question 6

Which equation correctly calculates the number of neutrons in an atom?

Accepted Answer

$$	ext{Number of neutrons} = 	ext{Mass number} - 	ext{Atomic number}$$

Question 7

A zinc atom has a mass number of 65 and an atomic number of 30. How many electrons does a neutral zinc atom have?

Accepted Answer

30

Question 8

Which of the following best explains why mass number does not appear in the periodic table?

Accepted Answer

Mass number applies only to individual atoms, not to all atoms of an element.

Question 9

An atom of barium (Ba) has 56 protons and 81 neutrons. What is its mass number?

Accepted Answer

137

Question 10

A potassium atom has 19 protons and 20 neutrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: 19, Mass number: 39

Question 11

Which of the following is true for all atoms of a given element?

Accepted Answer

They have the same number of protons.

Question 12

A neutral atom of chlorine has 17 protons. How many electrons does it have?

Accepted Answer

17

Question 13

Which of the following elements has an atomic number of 6?

Accepted Answer

Carbon

Question 14

A neutral atom of calcium has an atomic number of 20. What is its net charge?

Accepted Answer

Zero

Question 15

If an atom has a mass number of 14 and contains 6 protons, how many neutrons does it have?

Accepted Answer

8

Question 16

Which of the following best describes the relationship between atomic number and the periodic table?

Accepted Answer

Atomic number appears above the symbol of an element in the periodic table.

Question 17

A zinc atom has 37 neutrons. What is its mass number?

Accepted Answer

67

Question 18

Which of the following is the correct formula for calculating mass number?

Accepted Answer

$$	ext{Mass number} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 19

A neutral atom of gold (Au) has an atomic number of 79. How many electrons does it have?

Accepted Answer

79

Question 20

Which of the following statements is true regarding isotopes of an element?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Atoms and Elements: Atomic Number, Mass Number, and Composition

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