question

In the term trace element, the adjective trace means that

answer

the element is required in very small amounts.

question

Compared with 31P, the radioactive isotope 32P has

answer

one more neutron.

question

The reactivity of an atom arises from

answer

the existence of unpaired electrons in the valence shell.

question

Which statement is true of all atoms that are anions?

answer

The atom has more electrons than protons.

question

Which of the following statements correctly describes any chemical reaction that has reached equilibrium?

answer

The rates of the forward and reverse reactions are equal.

question

We can represent atoms by listing the number of protons, neutrons, and electrons-for example, 2p +, 2n 0, 2e - for helium. Which of the following represents the 18O isotope of oxygen?

answer

8p +, 10n 0, 8e -

question

The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound.

answer

H2S

question

What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6 → _____ C2H6O + _____ CO2

answer

2; 2

question

Which of the following bonds can form between atoms of equal electronegativity?

answer

Van der Waals interactions can form between atoms of equal electronegativity.

question

What does the term electron orbital describe?

answer

An electron orbital describes a three-dimensional space where an electron can be found 90% of the time.

question

Which statement about relative potential energy of electrons is correct?

answer

An electron in the 3 p orbital of the third electron shell has more potential energy than an electron in the 2 p orbital of the second electron shell.

question

Which statement about weak bonds is correct?

answer

Weak bonds are transient and easily reversible.

question

What happens when two atoms form a chemical bond?

answer

A chemical bond forms when two atoms transfer or share outer electrons to complete their outer shells.

question

Undersea deposits that contain metals such as copper, gold, and silver are collectively known as what?

answer

massive sulfides

question

The discovery of which of the following led to a drastic change in deep sea mining?

answer

black smokers

question

You are an explorer in search of deep sea metal deposits. Which of the following would likely be the best place to look?

answer

near volcanic fissures

question

Which of the following is true?

answer

The ores found in seabeds often have substantially higher purities than those found on land.

question

Your mining company wishes to export its metals to the country that consumes the most copper and gold. Where are you looking to send your products?

answer

China

question

Can you match these prefixes, suffixes, and word roots with their definitions?

answer

with or together with: co- not: non- equal: ios- many: poly- four: quad- (or quat-) against: anti- two: di- first: prim- single: mono- three: tri-

question

Can you match these prefixes, suffixes, and word roots with their definitions?

answer

first: proto- water: hydro- of neither gender or type: neutr- fat: lip- to fear: -phob loosening, split apart: -lysis to: ad- to love: -phil from, out of, remove: de-

question

A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____.

answer

element

question

Which of the following is a trace element required by most living organisms?

answer

magnesium

question

Given what you know about the human body, what do you think accounts for the high percentage of oxygen (65.0%)?

answer

The human body is made up mainly of water, and there is one oxygen atom in every water molecule.

question

About twenty-five of the ninety-two natural elements are known to be essential to life. Which four of these twenty-five elements make up approximately 96 percent of living matter?

answer

carbon, hydrogen, nitrogen, oxygen

question

Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants?

answer

iodine

question

Which of the following statements is FALSE?

answer

All life requires the same essential elements.

question

Which of the following are compounds?

answer

H2O and CH4, but not O2

question

What is the mass number of an ion with 109 electrons, 159 neutrons, and a +1 charge?

answer

269

question

Match each property to the appropriate subatomic particle.

answer

Proton: symbol P, +1 charge Neutron: symbol N, 0 charge Electron: symbol e, -1 charge

question

Sort the subatomic particles according to their masses.

answer

mass of ~1 amu: neutron & proton masss of ~1/2000: electron

question

What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?

answer

6

question

Which of these refers to atoms with the same atomic number but different atomic masses?

answer

These atoms are isotopes.

question

Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?

answer

10

question

An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?

answer

5

question

The innermost electron shell of an atom can hold up to _____ electrons.

answer

2

question

Which of these relationships is true of an uncharged atom?

answer

The number of protons is equal to the number of electrons.

question

What determines the types of chemical reactions that an atom participates in?

answer

the number of electrons in the outermost electron shell

question

Which of the following subatomic particles always has a positive charge?

answer

proton

question

Changing the number of _____ would change an atom into an atom of a different element.

answer

protons in an atom

question

The atoms of different phosphorus isotopes _____.

answer

have different numbers of neutrons

question

The type of bonding and the numbers of covalent bonds an atom can form with other atoms is determined by _____.

answer

the number of unpaired electrons in the valence shell

question

The mass number of an atom is 15, and its atomic number is 7. The atom probably has...

answer

8 neutrons in the nucleus.

question

Which statement is true of atoms?

answer

Electrons determine the atom's size.

question

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that ...

answer

the first shell shouldn't have 3 electrons.

question

Which statement is true of the energy levels of electrons in shells?

answer

The valence shell has higher energy than other occupied shells.

question

Which statement is true of the atom shown in the diagram?

answer

The atom has more than one valence electron. The atom is in the excited state. An electron will move from the outer to the inner shell.

question

Two atoms always represent the same element if they have ...

answer

the same number of protons.

question

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________.

answer

C; it has 6 protons.

question

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ...

answer

10 neutrons.

question

Radioactive decay is likely to occur when ...

answer

an atom has too many neutrons.

question

Which model most accurately represents the current view of the structure of the atom?

answer

Probability model

question

Which statement is most useful in explaining why chemists assign atoms to chemical elements by counting protons? The proton's negative charge holds electrons in the atom. 99% of the atom's mass consists of protons. Protons at the atom's surface determine the atom's behavior. The nucleus doesn't change in stable isotopes.

answer

None of these. Elements are defined by the number of protons.

question

Part A Carbon-14 (14C) is a radioactive isotope of carbon that decays to 14N at a constant rate. 14C is present in the atmosphere in small amounts at a constant ratio to both 13C and 12C, two stable isotopes of carbon. When carbon is taken up from the atmosphere by a plant during photosynthesis, 12C, 13C, and 14C isotopes are incorporated into the plant in the same proportions in which they are present in the atmosphere. These proportions remain the same in the tissues of an animal that eats the plant. While an organism is alive, the 14C in its body decays to 14N but is continually replaced by new carbon from the environment. Once an organism dies, it stops taking in new 14C, but the 14C in its tissues continues to decay, while the 12C in its tissues remains the same because it is not radioactive and does not decay. Thus, scientists can calculate how long the pool of original 14C has been decaying in a fossil by measuring the ratio of 14C to 12C and comparing it to the ratio of 14C to 12C present originally in the atmosphere. The fraction of 14C in a fossil compared to the original fraction of 14C can be converted to years because we know that the half-life of 14C is 5,730 years—in other words, half of the 14C in a fossil decays every 5,730 years. The graph below shows a standard graph of radioactive isotope decay. The red curve indicates the fraction of the radioactive isotope remaining (on the y-axis) over time in units of half-lives (on the x-axis). Recall that a half-life is the amount of time it takes for half of the radioactive isotope to decay.

answer

Time (half-lives): fraction of isotope remaining in fossil 1: 1/2 2: 1/4 3: 1/8 4: 1/16 5: 1/32 6: 1/64 7: 1/128 8: 1/256 9: 1/512 10: 1/1024

question

The graph below is the same as in Part A, but with the fractions converted to decimal values. For each decimal value, fill in the exponent to complete the scientific notation. Don't forget to indicate if the exponent should be negative (-). The first one has been done for you.

answer

Time (half-lives): fraction of isotope remaining in fossil 1: 10^-1 2: 10^-1 3: 10^-1 4: 10^-2 5: 10^-2 6: 10^-2 7: 10^-3 8: 10^-3 9: 10^-3 10: 10^-4

question

The graph you constructed so far applies to decay of any radioisotope. To calibrate it specifically to 14C, you need to calculate how many years must pass to reach the amount of remaining isotope for each point of the half-life curve. To calibrate the x-axis for 14C decay, you have to convert half-lives to number of years. Recall that 14C has a single half-life of 5,730 years. How many years make up 5 half-lives for 14C?

answer

28,650 years

question

The researchers found that the Neanderthal fossil had approximately 7.80 × 10-3 as much 14C as was present in the atmosphere around the living Neanderthal and the plants it ate. Approximately how many half-lives have passed since the Neanderthal died?

answer

7 half-lives

question

Using the 14C calibration on the x-axis, what is the approximate age of the Neanderthal fossil?

answer

40,110 years old

question

Recall that the analyzed fossil was found in the most historically recent (uppermost) layer containing Neanderthal bones of the excavated archeological site. Approximately when did Neanderthals become extinct at this location, according to the study?

answer

40,110 years ago or less

question

The researchers cite evidence that modern humans (H. sapiens) became established in the same region as the last Neanderthals approximately 39,000-42,000 years ago. What does this suggest about the possible overlap of Neanderthals and modern humans in the region?

answer

Neanderthals and modern humans may have lived in the same region for up to approximately 2,000 years, or they may not have overlapped at all.

question

Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14C be used to date dinosaur bones?

answer

No, the 14C present in the dinosaur when it died would decay too much to be measured after 65.5 million years.

question

Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils?

answer

Yes, after 65.5 million years only about one tenth of the 235U would have decayed, leaving plenty to measure in the fossils.

question

Knowing the atomic mass of an element allows inferences about which of the following?

answer

the number of protons plus neutrons in the element

question

In what way are elements in the same column of the periodic table the same? They have the same number of _____.

answer

electrons in their valence shells when neutral

question

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Therefore, which of the following can be true?

answer

Molybdenum atoms can have between 50 and 58 neutrons.

question

Carbon-12 is the most common isotope of carbon and has a mass number of 12. However, the average atomic mass of carbon found on a periodic table is slightly more than 12 daltons. Why?

answer

Some carbon atoms in nature have more neutrons.

question

Which of the following best describes the relationship between the atoms described below? Atom 1: 1 H 1 Atom 2: 3 H 1

answer

They are isotopes.

question

The atomic number of nitrogen is 7. Nitrogen-15 has a greater mass number than nitrogen-14 because the atomic nucleus of nitrogen-15 contains _____.

answer

8 neutrons

question

From its atomic number of 15, it is possible to predict that the phosphorus atom has _____.

answer

15 protons and 15 electrons

question

Fluorine has an atomic number of 9. Which of the following would you do to a neutral fluorine atom to complete its valence shell?

answer

add 1 electron

question

Magnesium has an atomic number of 12. What is the most stable charge for a magnesium ion?

answer

a +2 charge

question

Refer to the figure above (first three rows of the periodic table). What element has properties most similar to carbon?

answer

silicon

question

How many neutrons are present in the nucleus of a phosphorus-32 (32P) atom (see the figure above)?

answer

17

question

How many electrons will a single atom of sulfur with no charge and no bonds have in its valence shell (see the figure above)?

answer

6

question

Based on electron configuration, which of the elements in the figure above would exhibit a chemical behavior most like that of oxygen?

answer

sulfur

question

Which one of the atoms shown would be most likely to form a cation with a charge of +1?

answer

1st shell: two e- 2nd shell: one e-

question

Which one of the atoms shown would be most likely to form an anion with a charge of -1?

answer

1st shell: two e- 2nd shell: seven e-

question

Oxygen has an atomic number of 8 and most commonly, a mass number of 16. Thus, what is the atomic mass of an oxygen atom?

answer

approximately 16 daltons

question

If you change the number of neutrons in an atom, you create _____.

answer

an isotope

question

Can the atomic mass of an element vary?

answer

Yes. Adding or losing neutrons will change the atomic mass without forming a different element.

question

Which of the following is the best description of an atom's physical structure?

answer

Atoms are little bubbles of space with mass concentrated at the center of the bubble.

question

What type of bond is joining the two hydrogen atoms?

answer

covalent

question

A(n) _____ refers to two or more atoms held together by covalent bonds.

answer

molecule

question

This atom can form up to _____ single covalent bond(s).

answer

4

question

A(n) _____ bond joins these two oxygen atoms.

answer

double covalent

question

Which of these figures correctly illustrates the nature of the bonding of H2O?

answer

O has 4 electrons bonded to 2 H atoms. Each atom bond is 2 electrons. O atom has negative charge, H atoms have a positive charge.

question

What type of bond joins the carbon atom to each of the hydrogen atoms?

answer

single (nonpolar) covalent

question

Atoms with the same number of protons but with different electrical charges _____.

answer

are different ions

question

In salt, what is the nature of the bond between sodium and chlorine?

answer

ionic

question

What is the result of the animated process?

answer

a positively charged sodium ion and a negatively charged chlorine ion

question

An ionic bond involves _____.

answer

an attraction between ions of opposite charge

question

The brackets are indicating a(n) _____ bond.

answer

hydrogen

question

What name is given to the bond between water molecules?

answer

hydrogen

question

A carbon atom and a hydrogen atom form what type of bond in a molecule?

answer

nonpolar covalent bond

question

An ionic bond is formed when _____.

answer

one atom transfers an electron to another atom

question

Hydrogen bonding is most often seen _____.

answer

when hydrogen is covalently bonded to an electronegative atom

question

A cation with two units of charge has 10 neutrons and 8 protons. The ion also has ...

answer

6 electrons.

question

Which statement is true of the molecule shown here?

answer

It's both a cation and an anion.

question

The atoms shown here will become ions if they meet because ...

answer

atoms tend to avoid having a partly filled valence shell.

question

True or false: Ions may form by transferring an atomic nucleus (with or without electrons) to another molecule.

answer

True

question

When chemists and biologists want to show how atoms are bonded in a molecule, they usually use a ...

answer

structural formula.

question

A phrase that applies to covalent bonding and not other kinds of bonds is ...

answer

electron-sharing.

question

Covalent bonds hold atoms together because they ...

answer

(a) fill shells without giving atoms much charge. (b) bring electrons closer to protons.

question

In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively.

answer

4, 1, 2, 3

question

An atom's atomic number is 7. Its valence is most likely ...

answer

3

question

By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero?

answer

Shared electrons aren't always near oxygen.

question

In a double covalent bond, a carbon atom shares ...

answer

electrons in two orbitals.

question

The ammonia molecule in the diagram has the observed bond orientation because ... N has four pairs of electrons in the valence shell. N has 7 protons in its nucleus. electrons repel one another.

answer

All of the above.

question

Without making or breaking bonds, the pictured molecule can change its shape because ...

answer

rotation can occur around single bonds.

question

Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true?

answer

All the atoms lie in a plane. (b) atoms share electrons unequally.

question

Partial charges occur when ...

answer

atoms share electrons unequally.

question

To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add ...

answer

2 electrons.

question

Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?

answer

The valence shell needs 8 electrons.

question

An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?

answer

1

question

Which answer correctly ranks the atoms in terms of decreasing electronegativity (the highest electronegativity first)?

answer

O, N, C, H

question

Which atom in the pictured molecule will have the strongest partial positive charge?

answer

The C that's in C=O.

question

Dr. Haxton says the O-O bond is polar and the C-C bond is nonpolar. A good student would say ...

answer

Wrong again, Ralph. Both bonds are nonpolar.

question

Use your knowledge of electronegativity to pick out the most polar bond in the list below.

answer

O-H

question

If you want a molecule that is highly polar, look for one that contains:

answer

H-N

question

Compared to covalent bonds, ionic bonds ...

answer

rely much less on electron-sharing.

question

A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a _____.

answer

surface of hydrocarbons

question

A covalent chemical bond is one in which _____.

answer

outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals

question

What is the maximum number of covalent bonds that an oxygen atom with atomic number 8 can make with hydrogen?

answer

2

question

Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?

answer

Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.

question

Bonds between two atoms that are equally electronegative are _____.

answer

nonpolar covalent bonds

question

What results from an unequal sharing of electrons between atoms?

answer

a polar covalent bond

question

A covalent bond is likely to be polar when _____.

answer

one of the atoms sharing electrons is more electronegative than the other atom

question

What is the difference between covalent bonds and ionic bonds?

answer

Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms.

question

The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the formula for magnesium chloride?

answer

MgCl2

question

How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4?

answer

2

question

Which bond or interaction would be difficult to disrupt when compounds are put into water?

answer

covalent bonds between carbon atoms

question

Water molecules are attracted to one another by _____.

answer

hydrogen bonds

question

Van der Waals interactions may result when _____.

answer

electrons are not symmetrically distributed in a molecule

question

What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?

answer

6

question

What results from the chemical reaction illustrated above? The reactants have no charge.

answer

a cation with a net charge of +1 and an anion with a net charge of -1

question

What is the atomic number of the cation formed in the reaction illustrated above?

answer

11

question

What causes the shape of the molecule shown above?

answer

the shape of the sp3 hybrid orbitals of the electrons shared between the carbon and hydrogen atoms

question

How many electrons are involved in a single covalent bond?

answer

two

question

How many electrons are involved in a double covalent bond?

answer

four

question

If an atom has a charge of +1, which of the following must be true?

answer

It has one more proton than it does electrons.

question

Elements found on the left side of the periodic table contain outer shells that are _____; these elements tend to form _____ in solution.

answer

almost empty; cations

question

An atom has four electrons in its valence shell. What types of covalent bonds is it capable of forming?

answer

single, double, or triple

question

When are atoms most stable?

answer

when all of the electron orbitals in the valence shell are filled

question

When the atoms involved in a covalent bond have the same electronegativity, what type of bond results?

answer

a nonpolar covalent bond

question

Nitrogen (N) normally forms three covalent bonds with a valence of 5. However, ammonium has four covalent bonds, each to a different hydrogen (H) atom (H has a valence of 1). What do you predict to be the charge on ammonium?

answer

+1

question

You need to write down information about a molecule, but need to indicate only the type and number of atoms it contains. Which representation would work best?

answer

molecular formula

question

You need to represent a molecule to best illustrate the relative sizes of the atoms involved and their interrelationships. Which representation would work best?

answer

space-filling model

question

Chemical equilibrium is reached when _____.

answer

the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same

question

Which of the following is a chemical reaction? Melting ice. Making a hydrogen bond between a water molecule and a sugar molecule. Changing a carbon atom to a nitrogen atom by radioactive decay. Dissolving a lump of sugar in a cup of coffee.

answer

None of the above.

question

What kind of chemical reaction is shown in this animation below? Decomposition Isomerization Polymerization Addition

answer

None of the above.

question

Potential energy is always ... Which fact is most important in explaining how molecules convert thermal energy to activation energy (EA)?

answer

associated with position or arrangement.

question

Which of the following is true of activation energy?

answer

Molecules usually get it from thermal energy.

question

Which fact is most important in explaining how molecules convert thermal energy to activation energy (EA)?

answer

Distortion increases a molecule's potential energy.

question

Which statement is true of the transition state?

answer

(a) It can break apart to yield either reactants or products. (b) It is extremely unstable and lasts only an instant.

question

Which statement about the following reaction is true? 4 Fe + 3 O2 → 2 Fe2O3

answer

Four atoms of Fe react with 3 molecules of O2 to form 2 molecules of Fe2O3

question

Choose the appropriate balanced equation for the following chemical reaction. C6H6 + H2 → C6H12

answer

C6H6 + 3 H2 → C6H12

question

Choose the correct balanced equation for the following reaction. C8H18 + O2 → CO2 + H2O

answer

2 C8H18 + 25 O2 → 16 CO2 + 18 H2O

question

What is the molecular mass of caffeine (C8H10N4O2)?

answer

194.2

question

How many grams of water (H2O) are needed to react with 5.0 grams of ferric trichloride (FeCl3)? FeCl3 + 3 H2O → Fe(OH)3 + 3 HCl

answer

1.7 g H2O

question

How many grams of glucose would you need to make 1 liter of an aqueous 0.5M glucose solution? (Atomic masses: C = 12.01, H = 1.008, O = 16.00.)

answer

90.08 grams of glucose

question

Dr. Haxton says he has found a reaction that is truly irreversible. What would a good student say?

answer

Sorry, Doctor. All reactions are reversible.

question

Which statement is true of the relation between life and chemical equilibrium?

answer

(b) Living cells avoid chemical equilibrium by taking in energy and materials.

question

The reaction shown below is at equilibrium. What could you do to make this reaction produce more methyl benzoate?

answer

(a) Add more benzoic acid. (b) Remove some methanol (HOCH3).

question

In the equation ΔG = ΔH - TΔS, the change in the amount of disorder in the system is symbolized by ...

answer

ΔS

question

A chemist calculates that a certain reaction would result in ΔH = -9 kJ and TΔS = +1 kJ. What can you conclude?

answer

The reaction will occur spontaneously, because it decreases G.

question

For the reaction ATP + H2O → ADP + Pi, the change in standard free energy (ΔG∘) is -30.5 kJ/mol. From this information we can conclude that ...

answer

(a) the forward reaction will be spontaneous under standard conditions.

question

Under standard conditions the reversible reaction A + B → C + D has a ΔG∘ = -25 kJ/mol. What is ΔG when: T = 475 K, [A] = 0.5M, [B] = 0.2 M, [C] = 0.2 M, and [D] = 0.3 M?

answer

-27 kJ/mol

question

Which statement is true of the relationship between life and chemical equilibrium?

answer

(d) Living cells avoid chemical equilibrium by taking in energy and materials.

question

Catalysts speed reactions mainly by ...

answer

lowering EA.

question

Which of the following is true for this reaction? 3H2 + N2 2NH3

answer

Ammonia is being formed and decomposed simultaneously.

question

Which of the following correctly describes all chemical equilibrium?

answer

Forward and reverse reactions continue with no net effect on the concentrations of the reactants and products.

question

Which of the following correctly describes a reaction that has reached chemical equilibrium?

answer

The rate of the forward reaction is equal to the rate of the reverse reaction.

question

Ionic bonds form as a result of __________.

answer

attraction between ions that have opposite charges

question

Which of the following molecules has the shape of a completed tetrahedron?

answer

methane (CH4)

question

Which of the following four statements, if any, is true regarding essential elements and living organisms?

answer

Although all forms of life require iron, other elements are required only by certain species.

question

In which of the following will isotopes of an element always differ?

answer

atomic mass

question

Which of the following statements is true about chemical reactions?

answer

They involve the making and breaking of chemical bonds.

question

When the proton number and electron number are unequal, the atom or molecule __________.

answer

is an ion

question

The chemical characteristics or reactivity of an element depend mostly on the __________.

answer

number of electrons in its outermost shell

question

An atom that normally has __________ in its outer shell would NOT tend to form chemical bonds with other atoms.

answer

eight electrons

question

A hydrogen bond __________.

answer

is a weak chemical bond

question

Which of the following has negligible mass?

answer

electron

question

Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?

answer

the molecule's shape

question

Which of the following is a trace element?

answer

copper

question

A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. The respective number of neutrons, protons, and electrons that this carbon isotope has is __________.

answer

8, 6, and 6

question

Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?

answer

The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge.

question

Which of the following statements describes a reversible reaction that has reached chemical equilibrium?

answer

The rate of the reverse reaction equals the rate of the forward reaction.

question

Some groups of elements react chemically in similar ways. For example, the chemistry of sodium and the chemistry of lithium are similar. The chemistry of chlorine and the chemistry of iodine are also similar. These similarities in chemistry result when different elements have similar __________.

answer

numbers of outer-shell electrons

question

When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?

answer

a covalent bond

question

When do hydrogen bonds occur?

answer

when partial opposite charges on molecules come close enough to attract each other

question

Which of the following subatomic particles has appreciable mass and lacks a charge?

answer

neutron

question

What are the four most abundant elements found in living systems?

answer

hydrogen, oxygen, nitrogen, and carbon

question

There are __________ naturally occurring elements.

answer

92

question

Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal).

answer

three fewer neutrons

question

The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. Upon ionization, what would you expect the charge on the sulfate ion to be?

answer

-2

question

Refer to this summary equation of photosynthesis to complete the sentences about chemical bonds and reactions. 6 CO2 + 6 H2O → C6H12O6 + 6 O2

answer

The equation shows a [chemical reaction]-- the breaking and forming of chemical bonds that leads to a change in the composition of matter. In the equation, Co2 is a [reactant]. In the equation, C6H12O6 is a [product]. In 02, the type of bond that holds the two oxygen atoms together is a [nonpolar covalent bond]. In H2O, the type of bond that holds one of the hydrogen atoms to the oxygen atom is a [polar covalent bond]. The number of oxygen atoms on the left side of the equation is [equal to] the number of oxygen atoms on the right side.

question

A covalent bond is likely to be polar if __________.

answer

one of the atoms sharing electrons is much more electronegative than the other

question

What is the role of van der Waals interactions in biological molecules?

answer

Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules.

question

The number of protons in an uncharged atom __________.

answer

equals the number of electrons

question

Consider this statement: Concentrations of trace elements in an environment above what is required by organisms generally have no effect on those organisms. Which of the following is a valid response to this statement?

answer

False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.

question

The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?

answer

an atom with 20 protons, 21 neutrons, and 20 electrons

question

An uncharged atom of nitrogen (atomic number = 7) has __________.

answer

seven protons and seven electrons

Mastering Biology: Chapter 2

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