Ch 2

Question 1

What is an element?

Answer 1

A substance that cannot be broken down to other substances by chemical reactions.

Question 2

What is an atom?

Answer 2

The smallest unit of matter that still retains the properties of an element.

Question 3

What charge do neutrons have?

Answer 3

No electrical charge.

Question 4

What charge do protons have?

Answer 4

Positive charge.

Question 5

What charge do electrons have?

Answer 5

Negative charge.

Question 6

What forms the atomic nucleus?

Answer 6

Neutrons and protons.

Question 7

What is the mass of neutrons compared to protons?

Answer 7

Neutron mass and proton mass are almost identical.

Question 8

Where are electrons found in an atom?

Answer 8

In a cloud around the nucleus.

Question 9

What does an element contain?

Answer 9

Atoms with the same number of protons.

Question 10

What is an element’s atomic number?

Answer 10

The number of protons in its nucleus.

Question 11

What is an element’s mass number?

Answer 11

The sum of protons plus neutrons in the nucleus.

Question 12

How is atomic mass approximated?

Answer 12

By the mass number.

Question 13

What equals the atomic number?

Answer 13

The number of protons.

Question 14

Which is the smaller number between atomic number and mass number?

Answer 14

The atomic number.

Question 15

What are isotopes?

Answer 15

Two atoms of an element that have the same number of protons but differ in number of neutrons.

Question 16

What is the electron’s state of potential energy called?

Answer 16

Its energy level.

Question 17

Electrons are found in different _______ shells.

Answer 17

electron

Question 18

What characterizes each electron shell?

Answer 18

A characteristic average distance from the nucleus.

Question 19

What does the chemical behavior of an atom depend on?

Answer 19

The number of electrons in its outermost shell (valence shell)

The valence shell is crucial for determining how an atom interacts with others.

Question 20

What gives rise to the reactivity of an atom?

Answer 20

The presence of one or more unpaired electrons in the valence shell

Unpaired electrons are key in forming bonds with other atoms.

Question 21

What can atoms with incomplete valence shells do?

Answer 21

Share or transfer valence electrons with certain other atoms

This interaction is fundamental in forming chemical bonds.

Question 22

What happens when hydrogen loses or shares electrons?

Answer 22

It participates in forming chemical bonds

Hydrogen’s behavior is essential in many biological and chemical processes.

Question 23

What is a covalent bond?

Answer 23

The sharing of a pair of valence electrons by two atoms

Covalent bonds are a primary type of chemical bond.

Question 24

In a nonpolar covalent bond, how do atoms share electrons?

Answer 24

Equally

Nonpolar covalent bonds occur between atoms with similar electronegativities.

Question 25

In a polar covalent bond, how do atoms share electrons?

Answer 25

Unequally ## Footnote This unequal sharing results in partial charges on the atoms.

Question 26

What does non-equal sharing of electrons cause?

Answer 26

A partial positive or negative charge for each atom or molecule ## Footnote This is important for understanding molecular interactions.

Question 27

What can atoms do in relation to their bonding partners?

Answer 27

Strip electrons from their bonding partners ## Footnote This can lead to the formation of ions.

Question 28

What does covalent mean?

Answer 28

Shared electrons ## Footnote This term defines the nature of covalent bonds.

Question 29

What is a positive ion called?

Answer 29

Cation ## Footnote Cations are formed when atoms lose electrons.

Question 30

What is a hydrogen bond?

Answer 30

An attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom on a different molecule ## Footnote Hydrogen bonds are crucial for the properties of water and biological molecules.

Question 31

How does a molecule's shape relate to its function?

Answer 31

Molecular shape determines how biological molecules recognize and respond to one another ## Footnote The three-dimensional structure of a molecule is vital for its interactions.

Question 32

What is the cohesive behavior of water?

Answer 32

The molecules stay close together because of cohesion ## Footnote Cohesion is the property of water that allows it to form hydrogen bonds with itself.

Question 33

Define adhesion in the context of water.

Answer 33

The clinging of one substance to a different substance ## Footnote Adhesion helps water to interact with other materials, such as plant cells.

Question 34

What happens to water when it freezes?

Answer 34

Expansion upon freezing ## Footnote This property allows ice to float on water, which is crucial for aquatic life.

Question 35

How does water interact with heat?

Answer 35

Water absorbs heat from warmer air and releases stored heat to cooler air ## Footnote This property helps regulate temperature in the environment.

Question 36

What is a solution?

Answer 36

A liquid that is a homogeneous mixture of substances ## Footnote Solutions can consist of various solutes dissolved in a solvent.

Question 37

What is a solvent?

Answer 37

The dissolving agent of a solution ## Footnote In most biological contexts, water acts as the solvent.

Question 38

What is a solute?

Answer 38

The substance that is dissolved ## Footnote Examples of solutes include salts, sugars, and gases.

Question 39

What is an aqueous solution?

Answer 39

One in which water is the solvent ## Footnote A common example is sugar water.

Question 40

What keeps sodium and chloride ions from reforming an ionic bond in solution?

Answer 40

Water molecules ## Footnote Water's polarity helps to separate and stabilize these ions in solution.

Question 41

Define a hydrophilic substance.

Answer 41

A substance that has an affinity for water ## Footnote Hydrophilic substances are typically polar or charged.

Question 42

Define a hydrophobic substance.

Answer 42

A substance that does not have an affinity for water ## Footnote Hydrophobic substances are usually nonpolar and do not mix with water.

Question 43

The four emergent properties of water contribute to Earths suitability for life

Answer 43

Cohesive behaviors Ability to moderate temperature Expansion up on freezing Versatility as a solvent

Question 44

What does hydrophilic mean?

Answer 44

Likes water ## Footnote Hydrophilic substances are typically polar and can interact with water molecules.

Question 45

What does hydrophobic mean?

Answer 45

Dislikes water ## Footnote Hydrophobic substances are usually non-polar and do not interact well with water.

Question 46

What type of bonds are polar covalent bonds?

Answer 46

Bonds where electrons are shared unequally ## Footnote These bonds result in a molecule with a partial positive charge on one end and a partial negative charge on the other.

Question 47

What type of bonds are non-polar covalent bonds?

Answer 47

Bonds where electrons are shared equally ## Footnote Non-polar covalent bonds occur between atoms of the same element or between different elements with similar electronegativities.

Question 48

What does it mean when a substance dissolves?

Answer 48

It breaks down into smaller particles in a solvent ## Footnote Dissolving often involves interactions between solute and solvent molecules.

Question 49

Define an acid.

Answer 49

Any substance that increases the concentration of H+ ions in a solution ## Footnote Acids can donate protons (H+) to other substances.

Question 50

Define a base.

Answer 50

Any substance that reduces the concentration of H+ ions in a solution ## Footnote Bases can accept protons or donate hydroxide ions (OH-).

Question 51

How is the pH of a solution defined?

Answer 51

pH = -log[H+] ## Footnote pH is a measure of the acidity or basicity of a solution.

Question 52

What pH value indicates an acidic solution?

Answer 52

Less than 7 ## Footnote Acidic solutions have higher concentrations of H+ ions.

Question 53

What pH value indicates a basic solution?

Answer 53

Greater than 7 ## Footnote Basic solutions have lower concentrations of H+ ions and higher concentrations of OH- ions.

Question 54

What are buffers?

Answer 54

Substances that minimize changes in concentrations of H+ and OH- in a solution ## Footnote Buffers help maintain a stable pH in biological systems.

Question 55

How many covalent bonds can carbon form?

Answer 55

Four ## Footnote Carbon has four valence electrons, allowing it to form diverse and complex molecules.

Question 56

What are the building blocks for most organic molecules?

Answer 56

Carbon skeletons ## Footnote Carbon's ability to bond with many elements makes it fundamental to life.

Question 57

What is the significance of functional groups in molecules?

Answer 57

Functional groups determine the unique properties of each molecule. ## Footnote Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.

Question 58

True or False: Each molecule has the same functional groups.

Answer 58

False ## Footnote The number and arrangements of functional groups vary among different molecules.

Question 59

Fill in the blank: The number and arrangements of _______ in each molecule are unique properties.

Answer 59

functional groups ## Footnote Functional groups can include hydroxyl, carboxyl, amino, and several others.