2 Chemical Context of Life

Question 1

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 1

iodine

Question 2

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

Answer 2

Each element has a unique number of protons in its nucleus

Question 3

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

Answer 3

the number of protons plus neutrons in the element

Question 4

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

Answer 4

They have the same number of electrons in their valence shell.

Question 5

One difference between carbon-12 ( ) is that carbon-14 ( ) has

Answer 5

two more neutrons than carbon-12.

Question 6

An atom has 6 electrons in its outer shell. How many unpaired electrons does it have?

Answer 6

2

Question 7

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

Answer 7

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

Question 8

Atoms whose outer electron shells contain 8 electrons tend to

Answer 8

) be both chemically inert and gaseous at room temperature

Question 9

A covalent chemical bond is one in which

Answer 9

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

Question 10

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

Answer 10

nonpolar covalent bonds.

Question 11

What results from an unequal sharing of electrons between atoms?

Answer 11

a polar covalent bond

Question 12

A covalent bond is likely to be polar when

Answer 12

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

Question 13

What is the difference between covalent bonds and ionic bonds?

Answer 13

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

Question 14

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

Answer 14

a covalent bond

Question 15

Van der Waals interactions result when

Answer 15

electrons are not symmetrically distributed in a molecule.

Question 16

A group of molecular biologists is 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?

Answer 16

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

Question 17

1 mole (mol) = (Avogadro’s number)

Answer 17

6.02 x 10 ²³ molecule

Question 18

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

Answer 18

the number of unpaired electrons in the valence shell

Question 19

An ionic bond is formed when _____.

Answer 19

one atom transfers an electron to another atom

Question 20

Hydrogen bonding is most often seen _____.

Answer 20

when hydrogen is covalently bonded to an electronegative atom

Question 21

The tendency of an atom to pull electrons toward itself is referred to as its _____.

Answer 21

electronegativity