Unit 2

Question 1

An atom’s reactivity is determined by its _____.

Answer 1

electron configuration

Question 2

consists of two or more elements in a fixed ratio

Answer 2

compound

Question 3

The hydrogen atoms of a water molecule are bonded to the oxygen atom by ________ bonds

Answer 3

Polar covalent

Question 4

whereas neighboring water molecules are held together by ________ bonds.

Answer 4

hydrogen

Question 5

A covalent bond is likely to be polar if _____.

Answer 5

one of the atoms sharing electrons is much more electronegative

Question 6

Water can resist temperature change because _____.

Answer 6

heating water absorbs energy by disrupting the hydrogen bonds before evaporation can occur

Question 7

A material that resists a change in pH is called a(n) _____.

Answer 7

Buffer

Question 8

________ are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.

Answer 8

hydrogen bonds

Question 9

How do isotopes of an element differ?

Answer 9

by the atomic mass number

Question 10

Typically, nitrogen atoms are composed of electrons, protons, and neutrons. An isotope of nitrogen could

Answer 10

have more neutrons than the usual nitrogen atom.

Question 11

The number of _______ will equal the number of ________ in an electronically neutral atom.

Answer 11

electrons, protons

Question 12

In a water molecule, hydrogen and oxygen are held together by a ________ bond.

Answer 12

polar covalent

Question 13

The number of protons in an uncharged atom _____.

Answer 13

equals the total number of electrons in the orbital shells

Question 14

Which trace element needed by humans is commonly added to table salt?

Answer 14

Iodine

Question 15

Because the molecules of water are farther apart in ice than in liquid water, _____.

Answer 15

Ice is able to float

Question 16

A radioactive isotope is an isotope that

Answer 16

decays

Question 17

the breaking and forming of chemical bonds that leads to a change in the composition of matter.

Answer 17

chemical reaction

Question 18

the type of bond that holds the two oxygen atoms together is a

Answer 18

nonpolar covalent bond

Question 19

the type of bond that holds one of the hydrogen atoms to the oxygen atom is a

Answer 19

polar covalent

Question 20

When you add acid to a solution, _____.

Answer 20

the hydrogen ion concentration increases and lowers the pH

Question 21

1. The term for a solution with a low pH number, such as lemon juice or vinegar, is

Answer 21

acidic

Question 22

The term for a solution that has an equal concentration of H+ and OH- is

Answer 22

neutral

Question 23

The term for a solution with a high pH number, such as ammonia or bleach, is

Answer 23

Basic

Question 24

an acid is a compound that donates ______ to a solution.

Answer 24

H+

Question 25

The higher the pH number, the higher the concentration of __________ in a solution.

Answer 25

OH-

Question 26

A substance that accepts H+ when they are in excess and donates H+ when their concentration drops is called a(n)

Answer 26

buffer

Question 27

For most atoms, a stable configuration of electrons is attained when the atom __________.

Answer 27

has a completely filled outermost shell

Question 28

proton characteristics

Answer 28

charge +1, in the nucleus, determines atomic # and 1/2 determines atomic mass, is characteristic for each element

Question 29

Neutrons characteristics

Answer 29

no charge, in the nucleus, 1/2 determines atomic mass, may differ in isotopes

Question 30

electrons characteristics

Answer 30

charge is -1 and moves in an electron cloud.

Question 31

Which four elements are the primary components of important biological molecules, such as proteins, fats, and carbohydrates?

Answer 31

CHON
carbon, hydrogen, oxygen, and Nitrogen

Question 32

Water molecules stick to other water molecules because

Answer 32

hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules.

Question 33

what are the trace elements?

Answer 33

zinc, iodine: thyroide, fluoride:bad teeth , iron: anemic

Question 34

Two atoms of the same element must have the same number of _____.

Answer 34

protons

Question 35

Table salt is formed when

Answer 35

sodium donates its single outer electron to chlorine.

Question 36

In some areas, fluoride is added during the municipal water treatment process in order to help

Answer 36

to prevent tooth decay

Question 37

An ionic bond is shown below. It forms as a result of _____.

Answer 37

an attraction between atoms that have opposite charges

Question 38

A polar covalent bond _____.

Answer 38

results in an unequal sharing of electrons

Question 39

Sodium chloride (NaCl) dissolves in water because water molecules _____.

Answer 39

are polar

Question 40

The partial charges in this water molecule occur because of _____.

Answer 40

the unequal sharing of electrons between hydrogen and oxygen

Question 41

Which of the following best describes the atomic number of an atom?

Answer 41

the number of protons in the atom

Question 42

Ionic bonds form when _____.

Answer 42

one atom transfers an electron to another atom

Question 43

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

Answer 43

element

Question 44

The __________ of water molecules and the hydrogen bonds between water molecules explain most of water’s life-supporting properties.

Answer 44

polarity

Question 45

The ___________of water molecules to each other helps transport water from the roots to the leaves in plants.

Answer 45

cohesion

Question 46

When water warms or cools, ________ either break or form.

Answer 46

hydrogen bonds

Question 47

Thus, water absorbs or releases a great deal of
_______, helping to moderate temperatures.

Answer 47

heat

Question 48

Because ________is less dense than liquid water, it floats and protects lakes and oceans from freezing solid.

Answer 48

Ice

Question 49

Water is a versatile _________

Answer 49

solvent

Question 50

Blood and other biological fluids are aqueous solutions with a diversity of dissolved _________

Answer 50

solutes