Chapter Two

Question 1

atom?

Answer 1

the smallest piece of an element that retains the characteristics of that element

Question 2

element?

Answer 2

pure substance containing only one type of atom, cannot be broken down by chemical means

Question 3

molecule?

Answer 3

made up of atoms and is a stable association of atoms, can be composed of one or more elements

Question 4

compound?

Answer 4

made up of molecules of at least two different elements, NaCl is compound

Question 5

proton’s charge, mass, and location?

Answer 5

proton has a positive charge, a mass of 1 (amu) located inside the nucleus

Question 6

neutron’s charge, mass, location?

Answer 6

No charge, mass of 1 amu and it is located inside the nucleus

Question 7

Electron’s charge, location, and mass?

Answer 7

negative charge located in orbitals 90% of the time and the mass is 0 essentially

Question 8

atomic number?

Answer 8

the number of protons of the atoms, this identifies the element

Question 9

atomic weight?

Answer 9

is the average mass of all the isotopes of a particular element

Question 10

molecular weight?

Answer 10

the sum of all the atomic weights of all atoms in a molecule

Question 11

mass number?

Answer 11

the number of protons and neutrons in a atoms nucleus

Question 12

isotope?

Answer 12

an element with the same number of protons but different number of neutrons, so same element may have different mass number

Question 13

orbital?

Answer 13

region where an electron is located at least 90% of the time, can be occupied by a maximum of 2 electrons

Question 14

electron shell?

Answer 14

is the energy level

in the shell, orbitals are filled in a specific sequence

1st shell holds 2 electrons 1 orbital

2nd shell holds 8 electrons 4 orbitals

Question 15

valence shell?

Answer 15

the outermost shell, which determines how the atoms will behave

Question 16

when is an atom reactive / unstable?

Answer 16

when there are unpaired electrons in orbitals in the outer valence shell

Question 17

when is an atom stable / non-reactive?

Answer 17

when the valence shell is full

Question 18

covalent bonds?

Answer 18

when atoms share one or more pairs of electrons so that the valence shell is filled

they are very strong bonds - lots of energy to break them

can have single (one pair), double (two pairs) or triple (three pairs)

50-110 bond energy

Question 19

polar covalent?

Answer 19

when one atom has a greater electronegativity so the electrons shared in the bonds are more attracted to to that atom’s nucleus.

Question 20

non polar covalent?

Answer 20

when atoms have same electronegativity so electrons shared in the bond are shared equally.

Question 21

ionic bonds?

Answer 21

when one atom is much more electronegative, a complete transfer of electrons occurs

the result is two ions, one positively charged and one negatively charged

Ionic bonds are bonds formed from the electrical attractions of positive and negative ions

3-7 bond energy

Question 22

hydrogen bond?

Answer 22

is an attraction between the positive side and the negative side of another molecule (H2O) is a good example

3-7 bond energy

Question 23

van der Waals

Answer 23

occurs when adjacent atoms come close enough that the outer electron clouds just barely touch.

bond energy is 1

Question 24

redox reaction (oxidation-reduction) reaction?

Answer 24

when electrons are transferred between two molecules

if a molecule is reduced it gains a negative charge, or an electron (acceptor/agent that oxidizes)

if a molecule is oxidized it gains a positive charge by losing an electron (electron donor/agent that reduces)

Question 25

what bond is between one water molecule?

Answer 25

(polar) covalent because oxygen is much more electronegative than hydrogen

Question 26

what bond is between two water molecules?

Answer 26

hydrogen bonds form between water molecules when the polar ends of each other (negative oxygen) (positive hydrogen) are attracted to each other

Question 27

cohesion?

Answer 27

the tendency of water molecules to stick together because of hydrogen bonds

this results in high surface tension, and helps water move up plants

Question 28

adhesion?

Answer 28

is the attraction of water molecules to other molecule of a different type

Question 29

is water more dense as a liquid or as a solid?

Answer 29

water is more dense as a liquid because when water freezes the space between molecules increase and they move very slowly vs. when water is a liquid it moves freely and molecules to bond to each other easier

Question 30

acid?

Answer 30

an acid a molecule that releases hydrogen ions H+

strong acid is when all acid molecules dissociate completely (all release their H+)

weak acid is when not all of the molecules dissociate, so it can be reversible sometimes

Question 31

base?

Answer 31

molecules that accept H+

strong acids take all H+ ions

weak acids take some H+ ions

Question 32

Functional group of biological acids

Answer 32

COOH to COO + H+

Question 33

pH scale is based on what?

Answer 33

is based on the H+ concentration in moles/ L

Question 34

Acid pH?

Answer 34

Acids have high H+ concentration so they are zero on the scale

10^-1 = 1 on the scale

Question 35

base pH?

Answer 35

bases have low H+ concentration

10^-14 = 14 on the scale

Question 36

Buffer?

Answer 36

is a weak acid and its corresponding base

its helps maintain a constant pH

if a strong acid is added to the buffer solution not all the H+ in the solution will remain, some will be eaten up by the weak base.

as we discussed earlier, sometimes weak bases / weak acids can be reversed to keep everything balanced

Question 37

law of mass action?

Answer 37

addition of a reactant (acid) on one side of a reversible system drives the system in the direction that uses up that compound