Campbell Biology Chapter 2

Fluorine has an atomic number of 9 and a mass number of 19. how many electrons are needed to complete the valence shell of a fluorine atom?

1

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

15 protons and 15 electrons

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

2

an atom has 6 electrons in its outer shell. how many unpaired electrons does it have?

2

what is the maximum number of covalent bonds an element with atomic number 8 can make with hydrogen?

2

what is the maximum number of electrons in a single 2 p orbital of an atom?

2

what coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6 --> __________ C2H6O + ________ CO2

2,2

If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the most problems for this animal?

a surface made with carbon and hydrogen atoms covalently bonded together

Which of these systems is least likely to be at chemical equilibrium?

a test tube of living cells

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

ammonia is being formed and decomposed

electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is that

an electron may move to an electron shell farther away from the nucleus

oxygen has an atomic number of 8 and a mass number of 16. thus, what is the atomic mass of an oxygen atom?

approximately 16 daltons

atoms whose outer electron shells contain 8 electrons tend to

be both chemically inert and gaseous at room temperature

What factors are most important in determining which elements are most common in living matter?

both the relative abundances of the elements and the emergent properties of the compounds made from these elements

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?

carbon, hydrogen, nitrogen, oxygen

the nucleus of nitrogen atom contains 7 neutrons and 7 protons. which of the following is a correct statement concerning nitrogen?

the nitrogen atom has a mass number of 14 and an atomic mass of approximately 14 daltons

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

the number of protons plus neutrons in the element

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

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

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

the rates of the forward and reverse reactions are equal

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

they are isotopes

in what way are elements in the same column of the periodic table the same?

they have the same number of electrons in their valence shell

one different between carbon-12 (12/6 C) is the carbon-14 (14/6 C) has

two more neutrons than carbon-12

What bonding or interaction is most likely to occur among a broad array of molecules of various types (polar, non polar, hydrophilic, hydrophobic)?

van der waals interactions

Which of the following statements is false? 1.Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter 2. some trace elements are very abundant on Earth 3. virtually all organisms require the same elements in the same quantities 4. iron is an example of an element needed y all organisms 5. other than some trace elements, animals are mostly made up of the same elements as plants, in similar proportions

virtually all organisms require the same elements in the same quantities

O II C / \ H OH The illustration above shows a representation of formic acid. A formic acid molecule

will form hydrogen bonds with water molecules

the atomic number of each atom is given to the left of each of the elements below. Which of the atoms has the same valence as carbon (12/6 C)?

12/14 Si silicon

which of the following molecules contains the most polar covalent bond?

H2O

Which of the following would be regarded as compounds?

H2O and CH4 but not O2

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

H2S

a covalent bond is likely to be polar when

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

a covalent chemical bond is one in which

outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms

what results from an unequal sharing of electrons between atoms?

a polar covalent bond

Which of the following is not considered to be a weak molecular integration?

a covalent bond

Compared with ^31P, the radioactive isotope ^32P has

one more neutron

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

6

the atomic number of nitrogen is 7. nitrogen-15 is heavier than nitrogen-14 because the atomic nucleus of nitrogen-15 contains how many neutrons?

8

we can represent atoms by listing the number of protons, neutrons, and electrons: for example 2p+; 2n0; 2e- for helium. Which of the following represents the 18O isotope of oxygen?

8p+, 10n0, 8e-

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

MgCl2

In ammonium chloride salt (NH4Cl) the anion is a single chloride ion, Cl. What is the cation of NH4Cl?

NH4 with a charge of +1

A group of molecular biologists are trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?

a compound with the same three-dimensional shape as part of the hormone

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

covalent bond

In comparing covalent bonds and ionic bonds, which of the following would you expect?

covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly equal to completely unequal sharing of electrons

What is the different between covalent bonds and ionic bonds?

covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between atoms

Why is each element unique and different from other elements in chemical properties?

each element has a unique number of protons in its nucleus

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

each hydrogen atom has a partial positive charge, the nitrogen atom has a partial negative charge

Van der Waals interactions result when

electrons are not symmetrically distributed in a molecule

Which of the following correctly describes chemical equilibrium?

forward and reverse reactions continue with no effect on the concentrations of the reactants and products

Which of the following explains most specifically the attraction of water molecules to one another?

hydrogen bond

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?

iodine

the atomic number of neon is 10. Therefore, which of the following is most correct about an atom of neon?

it has 8 electrons in its outer electron shell and it is inert

an atom with atomic number 12 would have what type of chemical behavior in bonding with other elements?

it would form ions with a +2 charge

molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers of 92, 94, 95, 96, 97, 98, and 100. Therefore, which of the following can be true?

molybdenum atoms can have between 50 and 58 neutrons

two atoms appear to have the same mass number. these atoms

must have the same number of protons + neutrons

when two atoms are equally electronegative, they will interact to form

nonpolar covalent bonds

the organic molecules in living organisms have a measurably lower ratio of carbon-13/carbon-12, two stable isotopes of carbon that comprise approximately 1.1% and 98.9% of atmospheric carbon, respectively. What is a reasonable explanation for this phenomenon?

photosynthesis preferentially uses carbon dioxide molecules with carbon-12, and the lower carbon-13/carbon-12 ratio propagates through the food chain

Referring to the first three rows of the periodic table: If life arose on a planet where carbon is absent, which element might fill the role of carbon?

silicon

carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. a mole of carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why?

some carbon atoms in nature have more neutrons

phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a form of radioactive decay whereby a neutron turns into a proton and emits radiation in the form of an electron. What is the product of such radioactive decay of phosphorus-32?

sulfur-32 (atomic number 16)

which statement is true of all atoms that are anions?

the atom has more electrons than protons

In the term trace element, the modifier trace means that

the element is required in very small amounts

the precise weight of a mole of some pure elements like silicon (Si) can vary slightly from the standard atomic mass, or even from sample to sample. Why?

the element may have multiple stable isotopes, and the isotopic composition may vary from sample to sample

the reactivity of an atom arises from

the existence of unpaired electrons in the valence shell