Question 1

Which of the following best describes the difference between an element and an atom?

Accepted Answer

An element is a substance that cannot be broken down into other substances by chemical means, while an atom is the smallest unit of an element that retains its properties.

Question 2

Given an atom of element X with atomic number 17 and atomic mass 35, how many neutrons does it have?

Accepted Answer

$$35 - 17 = 18$$ neutrons

Question 3

Which of the following statements about protons, neutrons, and electrons is correct?

Accepted Answer

Protons and neutrons are found in the nucleus and have nearly equal mass, while electrons are found in orbitals and have much less mass.

Question 4

Which of the following best defines an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 5

A radioactive isotope becomes stable by which of the following processes?

Accepted Answer

Emitting radiation to lose energy and/or particles until it reaches a stable configuration.

Question 6

Which of the following bonds is formed by the equal sharing of electrons between two atoms?

Accepted Answer

Nonpolar covalent bond

Question 7

What is the main difference between an ionic bond and a polar covalent bond?

Accepted Answer

Ionic bonds involve the complete transfer of electrons, while polar covalent bonds involve unequal sharing of electrons.

Question 8

Which of the following best explains why water molecules are able to form hydrogen bonds with each other?

Accepted Answer

Water molecules have polar covalent bonds, resulting in partial charges that attract each other.

Question 9

Which of the following is true about the energy of electrons in an atom?

Accepted Answer

Electrons in shells further from the nucleus have higher potential energy than those closer to the nucleus.

Question 10

If a sodium atom (Na) has an atomic number of 11 and loses one electron to become Na$$^+$$, how many protons, neutrons (atomic mass = 23), and electrons does the ion have?

Accepted Answer

11 protons, 12 neutrons, 10 electrons

Question 11

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a partially positive hydrogen atom and a partially negative atom (such as oxygen or nitrogen) in another molecule.

Question 12

Which of the following is a trace element essential for human health?

Accepted Answer

Iodine

Question 13

Which of the following best describes the relationship between valence electrons and chemical reactivity?

Accepted Answer

Atoms with incomplete valence shells are more chemically reactive because they tend to gain, lose, or share electrons to achieve stability.

Question 14

Which of the following best explains why NaCl (table salt) dissolves easily in water?

Accepted Answer

The ionic bonds in NaCl are disrupted by the polar water molecules, which surround and separate the Na$$^+$$ and Cl$$^-$$ ions.

Question 15

Which of the following is a correct description of a chemical reaction?

Accepted Answer

A process in which reactants are transformed into products by breaking and forming chemical bonds.

Question 16

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule consists of two or more atoms bonded together, while a compound consists of two or more different elements bonded together.

Question 17

Which of the following best describes electronegativity?

Accepted Answer

The tendency of an atom to attract electrons toward itself in a chemical bond.

Question 18

Which of the following is true about the strength of ionic and hydrogen bonds in water?

Accepted Answer

Ionic bonds are weakened in water, while hydrogen bonds are also weak but can be significant in large numbers.

Question 19

Which of the following best explains how covalent bonds affect molecular shape?

Accepted Answer

Covalent bonds determine the spatial arrangement of atoms by the way orbitals overlap, resulting in specific molecular shapes.

Question 20

A molecule of methane (CH$$_4) $$has which type of bonds between carbon and hydrogen?

Accepted Answer

Nonpolar covalent bonds

Chapter 2 The Chemical Context of Life:REVIEW

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