Question 1

Which of the following statements best describes the difference between an element and a compound?

Accepted Answer

An element is a substance that cannot be broken down by chemical reactions, while a compound consists of two or more elements in a fixed ratio.

Question 2

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 3

What is the atomic number of an atom with 7 protons, 7 neutrons, and 7 electrons?

Accepted Answer

$$7$$

Question 4

Which of the following best explains why sodium (Na) and chlorine (Cl) form an ionic bond?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 5

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 6

A radioactive isotope of carbon has 6 protons and 8 neutrons. What is its mass number?

Accepted Answer

$$14$$

Question 7

Which of the following best describes a covalent bond?

Accepted Answer

The sharing of a pair of valence electrons between two atoms.

Question 8

Why is water (H$$_2O) $$considered a polar molecule?

Accepted Answer

The oxygen atom is more electronegative than the hydrogen atoms, causing unequal sharing of electrons.

Question 9

Which of the following elements makes up the highest percentage of body mass in humans?

Accepted Answer

Oxygen

Question 10

What is the main reason noble gases like helium are chemically inert?

Accepted Answer

They have a full valence shell of electrons.

Question 11

Which of the following best describes a hydrogen bond?

Accepted Answer

A bond formed when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Question 12

If an atom has an atomic number of 20 and a mass number of 40, how many neutrons does it have?

Accepted Answer

$$20$$

Question 13

Which of the following is a real-life example of a compound with properties different from its constituent elements?

Accepted Answer

Sodium chloride (NaCl), which is edible, formed from sodium (a reactive metal) and chlorine (a poisonous gas)

Question 14

Which of the following best explains why atoms form chemical bonds?

Accepted Answer

To achieve a full valence shell of electrons

Question 15

Which of the following is true about the mass of subatomic particles?

Accepted Answer

Neutrons and protons have nearly identical mass.

Question 16

A molecule of formic acid (CH$$_2O$_2) $$contains how many different elements?

Accepted Answer

$$3$$

Question 17

Which of the following best describes the difference between a polar and a nonpolar covalent bond?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing.

Question 18

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

Accepted Answer

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

Question 19

Which of the following best explains why radioactive isotopes are useful in medical imaging?

Accepted Answer

They decay spontaneously, emitting particles and energy that can be detected.

Question 20

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons determine the chemical behavior of an atom.

Chapter 2: The Chemical Context of Life – Study Notes

Study Guide - Practice Questions