Chapter 2

Question 1

the smallest unit of an element is the ___

Answer 1

atom

Question 2

the nucleus of the atom contains ___ and ___

Answer 2

protons; neutrons

Question 3

what are the four elements that make up living organisms?

Answer 3

carbon, nitrogen, oxygen, hydrogen

Question 4

the atomic number is the number of ___ in the atom

Answer 4

protons

Question 5

atomic mass equals ___

Answer 5

protons + neutrons

Question 6

isotopes are atoms of the same element that differ in the number of ___

Answer 6

neutrons

Question 7

an isotope that gives off energy, sometimes making the element unstable, is called a ___

Answer 7

radioisotope (radioactive isotope)

Question 8

radioisotopes can be used in medicine as ___

Answer 8

tracers in the body

Question 9

the energy emitted by ___ can be strong enough to kill harmful cells

Answer 9

radiation

Question 10

atoms interact with surrounding atoms through their ___

Answer 10

electrons

Question 11

like charges ___

Answer 11

repel

Question 12

opposite charges ___

Answer 12

attract

Question 13

slots of first three electron orbitals:

Answer 13

2, 8, 8

Question 14

the further away from the nucleus, the more ___ electrons get

Answer 14

potential energy

Question 15

when orbitals are filled, the atom is ___

Answer 15

stable

Question 16

atoms that have bonded together make up ___

Answer 16

molecules

Question 17

the three types of bonds in biochemical reactions are:

Answer 17

ionic, covalent, hydrogen

Question 18

atoms are initially ___ charged

Answer 18

neutrally

Question 19

when an atom gains an electron, it becomes ___ charged

Answer 19

negatively

Question 20

when an atom loses an electron, it becomes ___ charged

Answer 20

positively

Question 21

atoms become ___ when they gain or lose electrons

Answer 21

ions

Question 22

a cation is a ___ charged ion

Answer 22

positively

Question 23

an anion is a ___ charged ion

Answer 23

negatively

Question 24

type of bond where one atom gains an electron (becoming negative) and one atom loses an electron (becoming positive)

Answer 24

ionic

Question 25

type of bond where atoms (similar electronegativity) share one or more pairs of electrons

Answer 25

covalent *usually stronger than ionic bonds

Question 26

in nonpolar covalent bonds, electrons are shared ___

Answer 26

equally

Question 27

in polar covalent bonds, electrons are shared ___

Answer 27

unequally

Question 28

type of bond where positive end of one polar covalent molecule is attracted to the negative end of another covalent molecule

Answer 28

hydrogen *do not form molecules. only hold molecules together.

Question 29

is water electronegative?

Answer 29

yes

Question 30

___ substances are polar

Answer 30

hydrophilic

Question 31

___ substances are nonpolar

Answer 31

hydrophobic

Question 32

pH is the measure of free ___ in a solution

Answer 32

hydrogen

Question 33

acids ___ hydrogen when dissolved in water

Answer 33

donate

Question 34

bases ___ hydrogen when dissolved in water

Answer 34

accept

Question 35

___ keep pH toward neutral

Answer 35

buffers

Question 36

elements consist of only atoms with the same ___

Answer 36

atomic number