Question 1

Which of the following best distinguishes an element from a compound?

Accepted Answer

An element is a substance that cannot be broken down into other substances by chemical means, while a compound consists of two or more elements chemically combined in a fixed ratio.

Question 2

Which subatomic particles are found in the nucleus of an atom?

Accepted Answer

Protons and neutrons

Question 3

If an atom has an atomic number of 8 and a mass number of 18, how many neutrons does it have?

Accepted Answer

$$18 - 8 = 10$$ neutrons

Question 4

Which statement correctly describes the difference between atomic number and mass number?

Accepted Answer

Atomic number is the number of protons in an atom, while mass number is the sum of protons and neutrons.

Question 5

Two isotopes of the same element differ in which of the following?

Accepted Answer

Number of neutrons

Question 6

Which of the following best explains why the electron configuration of an atom influences its chemical behavior?

Accepted Answer

The arrangement of electrons, especially in the outermost shell, determines how an atom interacts and bonds with other atoms.

Question 7

Which of the following bonds involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 8

How many electrons are shared in a double covalent bond?

Accepted Answer

$$2 	imes 2 = 4$$ electrons

Question 9

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally between two atoms, resulting in partial charges.

Question 10

Which of the following is a key difference between hydrogen bonds and covalent bonds?

Accepted Answer

Hydrogen bonds are weak attractions between molecules, while covalent bonds involve the sharing of electrons within a molecule.

Question 11

A sodium atom (Na) has 11 protons and 12 neutrons. What is its mass number?

Accepted Answer

$$11 + 12 = 23$$

Question 12

Which of the following statements about ionic bonds is correct?

Accepted Answer

Ionic bonds are formed when one atom donates an electron to another atom, resulting in oppositely charged ions that attract each other.

Question 13

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons and partial charges on the molecule.

Question 14

Which of the following is true about the valence of an atom?

Accepted Answer

Valence is the number of electrons an atom needs to gain or lose to achieve a full outer shell.

Question 15

A carbon atom has 6 protons, 6 neutrons, and 6 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: $$6$$, Mass number: $$12$$

Question 16

Which of the following best describes the octet rule and its significance in chemical bonding?

Accepted Answer

Atoms tend to form bonds to achieve eight electrons in their outermost shell, resulting in greater stability.

Question 17

Which of the following scenarios best illustrates the formation of an ionic compound?

Accepted Answer

A sodium atom donates an electron to a chlorine atom, forming Na$$^+$$ and Cl$$^-$$ ions that attract each other to form NaCl.

Question 18

Which of the following is a correct statement about nonpolar covalent bonds?

Accepted Answer

Electrons are shared equally between the two atoms.

Question 19

Which of the following best explains why isotopes of an element have similar chemical properties?

Accepted Answer

They have the same number of protons and electrons, which determine chemical behavior.

Question 20

A molecule of methane (CH$$_4) $$contains how many single covalent bonds?

Accepted Answer

$$4$$ single covalent bonds

Study Notes: The Chemical Context of Life

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