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

Question 1

Which of the following statements is always true for a neutral atom of an element?

Accepted Answer

The number of protons equals the number of electrons.

Question 2

An atom has 26 protons, 29 neutrons, and 26 electrons. Which element is it?

Accepted Answer

Iron ($\mathrm{Fe}$)

Question 3

A neutral atom of uranium has an atomic number of 92. How many electrons does it have?

Accepted Answer

$92$

Question 4

Which of the following can always be used to identify an element uniquely?

Accepted Answer

Number of protons

Question 5

A charged atom (ion) has 86 electrons, 125 neutrons, and 82 protons. What is the symbol for this ion?

Accepted Answer

$\mathrm{Pb}^{4-}$

Question 6

Given the atomic mass of fluorine is approximately $18.998$, what is the number of neutrons in a typical atom of fluorine?

Accepted Answer

$10$

Question 7

Which element has 2 electrons in its neutral atom?

Accepted Answer

Helium ($\mathrm{He}$)

Question 8

A student is given only the number of neutrons in an atom. Can they always determine the element?

Accepted Answer

No

Question 9

If an atom has 53 protons and 74 neutrons, what is its mass number?

Accepted Answer

$127$

Question 10

Which of the following is the correct calculation for the number of neutrons in an atom?

Accepted Answer

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

Question 11

A sample of barium has an atomic mass of $137.33$. What is the number of neutrons in its most common isotope?

Accepted Answer

$81$

Question 12

Which of the following elements has no neutrons in its most common isotope?

Accepted Answer

Hydrogen ($^1\mathrm{H}$)

Question 13

A neutral atom of chlorine has an atomic number of $17$ and a mass number of $35$. How many neutrons does it have?

Accepted Answer

$18$

Question 14

Which of the following statements is true about isotopes?

Accepted Answer

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

Question 15

A neutral atom of magnesium has an atomic number of $12$ and a mass number of $24$. What is the number of electrons and neutrons, respectively?

Accepted Answer

$12$ electrons, $12$ neutrons

Question 16

Which of the following is NOT sufficient to always determine the identity of an element?

Accepted Answer

Number of neutrons

Question 17

A neutral atom of bismuth has an atomic number of $83$ and a mass number of $209$. How many neutrons does it have?

Accepted Answer

$126$

Question 18

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

Accepted Answer

The atomic number is equal to the number of protons in the nucleus.

Question 19

A neutral atom of antimony ($\mathrm{Sb}$) has an atomic number of $51$. How many electrons does it have?

Accepted Answer

$51$

Question 20

If you are given only the number of electrons in a neutral atom, can you always determine the element?

Accepted Answer

Yes

Atoms: Structure, Symbols, and Subatomic Particles

Study Guide - Practice Questions