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

Question 1

Which of the following statements best describes an atom?

Accepted Answer

An atom is the smallest unit of a chemical element that retains the properties of that element.

Question 2

Which subatomic particle determines the atomic number of an element?

Accepted Answer

Proton

Question 3

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

$$23 - 11 = 12$$

Question 4

Which of the following is true about electrons in the same energy shell?

Accepted Answer

They have the same energy.

Question 5

Which element is NOT one of the six most abundant elements in living organisms (CHNOPS)?

Accepted Answer

Calcium

Question 6

What is the charge and location of a neutron in an atom?

Accepted Answer

No charge, located in the nucleus

Question 7

According to the octet rule, how many electrons are needed to fill the valence shell of most atoms (except hydrogen and helium)?

Accepted Answer

8

Question 8

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

Their valence shells are fully occupied.

Question 9

How many valence electrons does a neutral oxygen atom have?

Accepted Answer

6

Question 10

Which of the following is a negatively charged particle found outside the nucleus?

Accepted Answer

Electron

Question 11

If an atom has 15 protons, 16 neutrons, and 15 electrons, what is its mass number?

Accepted Answer

$$15 + 16 = 31$$

Question 12

Which property is used to organize elements in the periodic table?

Accepted Answer

Atomic number

Question 13

A carbon atom has an atomic number of 6. How many electrons does it have in a neutral state?

Accepted Answer

6

Question 14

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 15

Which of the following is the correct formula to calculate the number of neutrons in an atom?

Accepted Answer

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

Question 16

Which of the following elements is most likely to form ions to achieve a full octet?

Accepted Answer

Oxygen

Question 17

Which statement best explains why an atom is electrically neutral?

Accepted Answer

It has equal numbers of protons and electrons.

Question 18

Which of the following is a real-world application of the octet rule?

Accepted Answer

Sodium donates one electron to chlorine to form table salt (NaCl).

Question 19

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

Accepted Answer

Elements are arranged in order of increasing atomic number.

Question 20

Which of the following is true about valence electrons?

Accepted Answer

They are found in the outermost shell of an atom.

Atoms: The Smallest Unit of Matter – Structure, Properties, and the Octet Rule

Study Guide - Practice Questions