BIO 21 TEST 1 STUDY GUIDE EXAM
QUESTIONS WITH COMPLETE
SOLUTIONS
Understand subatomic structure, including how electron density affects an atom's ability
to interact with another atom. - ANSWER-electrons have negligible mass. Electrons of
an atom have potential energy due to their distance from the nucleus.
Quantify atomic mass using units such as Daltons and moles - ANSWER-Unit of
measurement for atomic mass
Also known as atomic mass unit (amu)
One dalton (Da)equals 1/12 the mass of a
Relate atomic structure to the periodic table of the elements - ANSWER-The diagram
shows a section of the periodic table, with the elements arranged as usual in the order
of their atomic number, from 2 to 20. The red numbers below each chemical symbol
show its electronic structure. ... Each element in a group therefore has the same
number of electrons in its highest occupied energy level.
Explain the discrete energy levels in which electrons orbit the nucleus of an atom. -
ANSWER-The electrons in an atom's outermost energy level are its valence electrons.
Atoms with a completely filled outermost energy level are nonreactive, or inert (helium,
neon, argon).Atoms in which the outermost energy level is not completely filled with
electrons are chemically reactive (hydrogen)
Compare and contrast interactions known as covalent, ionic, and H+ bonding. -
ANSWER-1.Form between atoms whose outer electron shells are not full. Covalent
bonds are strong chemical bonds, because the shared electrons behave as if they
belong to each atom
2.Hydrogen bonds are attractions between partially positive hydrogen atoms (sharing
electrons unequally with oxygen, nitrogen, or sulfur) and partially negative atoms
sharing in a different covalent bond
3.Ionic bonds result from electrical attractions between atoms that gain or lose valence
electrons completely (ions)
Explain the concept of electronegativity and how it contributes to the formation of polar
and nonpolar covalent bonds. - ANSWER-Electronegativity is the measure of an atom's
attraction for the electrons it shares in a chemical bond with another atom
Covalent bonds can be symmetrical or asymmetrical, depending on the difference in
electronegativity between the bonded atoms
The more electronegative an atom is, the more strongly it attracts shared electrons
n a nonpolar covalent bond, electrons are shared equally.in a polar covalent bond,
electrons are shared unequally
, Describe the properties of water that make it an ideal solvent for biological reactions. -
ANSWER-small, polar molecule that has great intermolecular cohesion; more cohesion
than other nonmetals that are liquid at normal temperatures.
Relate how the structure of water leads to hydrogen bonds. - ANSWER-As a result of
water's polarity, each water molecule attracts other water molecules because of the
opposite charges between water molecules, forming hydrogen bonds.
Describe how H+ bonding determines many properties of water. - ANSWER-One of
water's important properties is that it is composed of polar molecules: the hydrogen and
oxygen within water molecules (H2O) form polar covalent bonds. Water generates
charges because oxygen is more electronegative than hydrogen,
Describe water's cohesive and adhesive properties. - ANSWER-In cohesion, water
molecules are attracted to each other (because of hydrogen bonding), keeping the
molecules together at the liquid-gas (water-air) interface, although there is no more
room in the glass.
these cohesive forces are related to water's property of adhesion, or the attraction
between water molecules and other molecules.
Explain the relevance of water's unusual properties for living systems. - ANSWER-
These forces create a "pull" on the water column. This pull results from the tendency of
water molecules evaporating on the plant's surface to stay connected to water
molecules below them, and so they are pulled along. Plants use this natural
phenomenon to help transport water from their roots to their leaves. Without these
properties of water, plants would be unable to receive the water and the dissolved
minerals they require. In another example, insects such as the water strider, as Figure
shows, use the water's surface tension to stay afloat on the water's surface layer and
even mate there.
Understand the dissociation products of water. - ANSWER-Unlike ionic compounds,
such as sodium chloride, they are not ionized before they dissociate; they accomplish
ionization and dissociation at the same time. Water dissociates into positively charged
hydrogen ions (H+or protons) and negative hydroxide ions (OH-)H2O ↔ H++ OH-.The
reaction is reversible.In pure water, concentrations of H+and OH-are equal: 10-7M
Explain the nature of acids and bases, and their relationship to the pH scale. -
ANSWER-1.Acids are proton donors that release H+(and anions) when they are
dissolved in water, increasing the H+concentration
2.Bases are proton acceptors that reduce the H+concentration of a solution; most
release a hydroxide ion (OH-) and a cation
3.The concentration of H+ions in a water solution compared with the concentration of
OH-ions determines the acidityof the solution. Acidity is measured using the pH scale -
ranging from 0 to 14 -based on logarithms of the number of H+ions in solution pH = -
log10[H+]
QUESTIONS WITH COMPLETE
SOLUTIONS
Understand subatomic structure, including how electron density affects an atom's ability
to interact with another atom. - ANSWER-electrons have negligible mass. Electrons of
an atom have potential energy due to their distance from the nucleus.
Quantify atomic mass using units such as Daltons and moles - ANSWER-Unit of
measurement for atomic mass
Also known as atomic mass unit (amu)
One dalton (Da)equals 1/12 the mass of a
Relate atomic structure to the periodic table of the elements - ANSWER-The diagram
shows a section of the periodic table, with the elements arranged as usual in the order
of their atomic number, from 2 to 20. The red numbers below each chemical symbol
show its electronic structure. ... Each element in a group therefore has the same
number of electrons in its highest occupied energy level.
Explain the discrete energy levels in which electrons orbit the nucleus of an atom. -
ANSWER-The electrons in an atom's outermost energy level are its valence electrons.
Atoms with a completely filled outermost energy level are nonreactive, or inert (helium,
neon, argon).Atoms in which the outermost energy level is not completely filled with
electrons are chemically reactive (hydrogen)
Compare and contrast interactions known as covalent, ionic, and H+ bonding. -
ANSWER-1.Form between atoms whose outer electron shells are not full. Covalent
bonds are strong chemical bonds, because the shared electrons behave as if they
belong to each atom
2.Hydrogen bonds are attractions between partially positive hydrogen atoms (sharing
electrons unequally with oxygen, nitrogen, or sulfur) and partially negative atoms
sharing in a different covalent bond
3.Ionic bonds result from electrical attractions between atoms that gain or lose valence
electrons completely (ions)
Explain the concept of electronegativity and how it contributes to the formation of polar
and nonpolar covalent bonds. - ANSWER-Electronegativity is the measure of an atom's
attraction for the electrons it shares in a chemical bond with another atom
Covalent bonds can be symmetrical or asymmetrical, depending on the difference in
electronegativity between the bonded atoms
The more electronegative an atom is, the more strongly it attracts shared electrons
n a nonpolar covalent bond, electrons are shared equally.in a polar covalent bond,
electrons are shared unequally
, Describe the properties of water that make it an ideal solvent for biological reactions. -
ANSWER-small, polar molecule that has great intermolecular cohesion; more cohesion
than other nonmetals that are liquid at normal temperatures.
Relate how the structure of water leads to hydrogen bonds. - ANSWER-As a result of
water's polarity, each water molecule attracts other water molecules because of the
opposite charges between water molecules, forming hydrogen bonds.
Describe how H+ bonding determines many properties of water. - ANSWER-One of
water's important properties is that it is composed of polar molecules: the hydrogen and
oxygen within water molecules (H2O) form polar covalent bonds. Water generates
charges because oxygen is more electronegative than hydrogen,
Describe water's cohesive and adhesive properties. - ANSWER-In cohesion, water
molecules are attracted to each other (because of hydrogen bonding), keeping the
molecules together at the liquid-gas (water-air) interface, although there is no more
room in the glass.
these cohesive forces are related to water's property of adhesion, or the attraction
between water molecules and other molecules.
Explain the relevance of water's unusual properties for living systems. - ANSWER-
These forces create a "pull" on the water column. This pull results from the tendency of
water molecules evaporating on the plant's surface to stay connected to water
molecules below them, and so they are pulled along. Plants use this natural
phenomenon to help transport water from their roots to their leaves. Without these
properties of water, plants would be unable to receive the water and the dissolved
minerals they require. In another example, insects such as the water strider, as Figure
shows, use the water's surface tension to stay afloat on the water's surface layer and
even mate there.
Understand the dissociation products of water. - ANSWER-Unlike ionic compounds,
such as sodium chloride, they are not ionized before they dissociate; they accomplish
ionization and dissociation at the same time. Water dissociates into positively charged
hydrogen ions (H+or protons) and negative hydroxide ions (OH-)H2O ↔ H++ OH-.The
reaction is reversible.In pure water, concentrations of H+and OH-are equal: 10-7M
Explain the nature of acids and bases, and their relationship to the pH scale. -
ANSWER-1.Acids are proton donors that release H+(and anions) when they are
dissolved in water, increasing the H+concentration
2.Bases are proton acceptors that reduce the H+concentration of a solution; most
release a hydroxide ion (OH-) and a cation
3.The concentration of H+ions in a water solution compared with the concentration of
OH-ions determines the acidityof the solution. Acidity is measured using the pH scale -
ranging from 0 to 14 -based on logarithms of the number of H+ions in solution pH = -
log10[H+]
