Ch. 2: The Chemical Context of Life

Question 1

Matter

Answer 1

anything that has mass and takes up space

Question 2

Pure Substance

Answer 2

elements and compounds

Question 3

Element

Answer 3

cannot be broken down further (ex: H)

Question 4

Compound

Answer 4

a substance composed of two or more elements; can be broken down further (ex: H2O)

Question 5

Trace Elements

Answer 5

required in only minute (very small) quantities

Question 6

Atom

Answer 6

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

Question 7

Which elements compose ~96% of living matter?

Answer 7

Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N)

Question 8

Subatomic Particles

Answer 8

particles that compose atoms; protons, neutrons, electrons

Question 9

Neutron

Answer 9

neutral charge

Question 10

Proton

Answer 10

positive charge

Question 11

Electron

Answer 11

negative charge

Question 12

Atomic Nucleus

Answer 12

dense core where protons and neutrons are packed tightly; electrons surround an atom, forming a cloud

Question 13

What is the atomic mass unit (amu)?

Answer 13

Dalton

Question 14

Atomic Number

Answer 14

number of PROTONS in an element; tells the number of protons AND electrons in an element (because they balance each other out, so must be equal); ex: 2He means 2 protons in helium nucleus (Helium is second element on periodic table)

Question 15

What does the atomic number dictate?

Answer 15

The location of an element on the periodic table (ex: Oxygen has an atomic number of 8, making it the 8th element on the periodic table)

Question 16

Mass Number

Answer 16

total number of protons and neutrons in a nucleus

Question 17

How do you find the number of neutrons?

Answer 17

Subtract the atomic number from the mass number (ex: 4/2 He, 4-2 = 2 neutrons)

Question 18

Atomic Mass

Answer 18

total mass of an atom

Question 19

What will all isotopes always have the same number of?

Answer 19

they will always have the same number of protons as the original element

Question 19

Isotopes

Answer 19

different atomic forms of the SAME element

Question 20

Radioactive Isotope

Answer 20

nucleus decays spontaneously, releasing particles and energy, which can serve as tracers to track atoms

Question 21

Half-Life

Answer 21

“parent” isotope decays into its “daughter” isotope at a FIXED rate; the time it takes for 50% of the isotope to decay

Question 22

How does potential energy vary with distance? (relating to electrons and nucleus)

Answer 22

the more distant an electron is from the nucleus, the greater potential energy there is

Question 23

Electron Shells

Answer 23

each has a characteristic average distance to the nucleus; the first shell closest to the nucleus has the lowest potential energy

Question 24

How do electrons move between shells?

Answer 24

when an electron absorbs energy, it moves to a shell farther out from nucleus; when it loses energy, it moves to a shell closer to the nucleus

Question 25

How many electrons can the first shell hold?

Answer 25

No more than 2; the maximum is 2

Question 26

How many electrons can the second shell hold?

Answer 26

a maximum of 8

Question 27

Which shell is most responsible for the chemical behavior of an atom?

Answer 27

the outermost shell (valence shell) and the number of electrons it has

Question 28

Valence electrons

Answer 28

electrons on the outermost shell

Question 29

Valence shell

Answer 29

outermost electron shell

Question 30

What happens when an atom has a completed valence shell?

Answer 30

it is unreactive; inert

Question 31

Orbital

Answer 31

the 3-dimensional space where an electron is found 90% of the time; a component of electron shell

Question 32

How many electrons can occupy a single orbital?

Answer 32

no more than 2

Question 33

How many electrons can the four orbitals of the second shell hold?

Answer 33

8 electrons

Question 34

Chemical Bond

Answer 34

attraction that holds atoms together

Question 35

Covalent Bond

Answer 35

the sharing of a pair of valence electrons by two atoms

Question 36

Molecule

Answer 36

two or more atoms held together by covalent bonds

Question 37

Single Bond

Answer 37

one pair of shared electrons

Question 38

Double Bond

Answer 38

2 pairs of shared electrons

Question 39

Valence

Answer 39

bonding capacity; usually equal to the number of electrons required to complete the atom's outermost (valence) shell

Question 40

What does valence generally determine?

Answer 40

how many covalent bonds that atom will form

Question 41

Electronegativity

Answer 41

the attraction of a particular atom for the electrons of a covalent bond; atoms attract shared bonding electrons to varying degrees

Question 42

How does electronegativity affect the pull of shared electrons?

Answer 42

The more electronegative an atom is, the more strongly it pulls shared electrons toward ITSELF; it wants to bring them closer

Question 43

Nonpolar Covalent Bond

Answer 43

a covalent bond between two atoms of the SAME element in which the electrons are shared EQUALLY since the atoms have the same electronegativity

Question 44

Polar Covalent Bond

Answer 44

when one atom is bonded to a more electronegative atom, so the electrons of the bond are not shared equally (they are pulled closer to the atom with greater electronegativity)

Question 45

Ions

Answer 45

atoms or molecules that have an electrical charge

Question 46

Cation

Answer 46

ion w/ positive charge

Question 47

Anion

Answer 47

ion w/ negative charge

Question 48

Ionic Bond

Answer 48

attraction between cations and anions; any two ions of opposite charge can form an ionic bond

Question 49

Ionic Compounds (Salts)

Answer 49

compounds formed by ionic bonds; they do not consist of molecules

Question 50

How does an ion become a cation?

Answer 50

loses an electron

Question 51

How does an ion become an anion?

Answer 51

gain an electron

Question 52

Hydrogen Bond

Answer 52

noncovalent attraction between a hydrogen atom and an electronegative atom

Question 53

van der Waals interactions

Answer 53

occur only when atoms and molecules are very close together, enables atoms and molecules to stick to each other; individually weak

Question 54

Reactant

Answer 54

starting material in a chemical reaction

Question 55

Product

Answer 55

resulting material in a chemical reaction

Question 56

What happens during chemical reactions?

Answer 56

matter is conserved; it cannot be destroyed or created, only electrons can be rearranged

Question 57

Chemical Equilibrium

Answer 57

the point at which the reactions offset one another EXACTLY