chem exam #1 - sept 20

Question 1

subatomic particles

Answer 1

the neutrons, protons and electrons in an atom

Question 2

jj thompson and the cathde ray tube (1897)

Answer 2

• cathode ray tube (glass tube with most of air removed) is connected to power supply, this generates cathode rays (streams of e-)
• cathode ray passed into region beyond power supply

Question 3

thompson found that by applying electric or magnetic fields…

Answer 3

he could bend the cathode rays
- this allowed him to calculate mass-to-charge ratio of e- (plum pudding model

Question 4

robert millikans oil drop experiment

Answer 4

• generated very tiny oil drops that fell toward a neg-charged plate
• x-ray beam generates e- that stick to the oil drops

Question 5

R.M. -1) by changing the charge on the plate he could…
- 2) by using mass-charge ratio from thompson…

Answer 5

1) - change the rate at which the oil drops fell
- determined charge of an e- (-1.602 x10^-19 coulomb)
2) calculated mass of an e- (9.109 x10 ^-31)

Question 6

1896, Henri Becquerel discovered…

Answer 6

radiation being emitted by the mineral pitchblende

Question 7

becquerel, curie’s, and rutherford discovered it was…

Answer 7

several types of radiation

Question 8

rutherford found beta particles

Answer 8

(B) - equivalent in mass and charge to high energy electron

Question 9

alpha particles

Answer 9

(fish) - equivalent in charge to 4He nucleus (2 protons, 2 neutrons)

Question 10

alpha and beta particles get deflected in…

Answer 10

opposite directions by electric fields

Question 11

rutherford gold foil experiment 1909

Answer 11

• had two graduate students test the plum pudding model
• bombard thin gold sheet w alpha particles

Question 12

if the plum pudding model was correct…

Answer 12

the alpha particles should pass right through with some minor deflection

Question 13

results of gold foil

Answer 13

• about 1 in 8000 particles deflected an average of 90 degrees, some bounced straight back (some fraction of alpha particles encountered a region of high pos. charge and mass)

Question 14

1920, consensus that all nuclei contain …

Answer 14

protons

Question 15

1932, neutrons were characterized in the…

Answer 15

nucleus

Question 16

each proton and neutron has a mass of…

Answer 16

1 unified atomic mass unit, also called daltons (Da)

Question 17

isotopes

Answer 17

atoms of the same element that have the same # of protons, but a diff # of neutrons on nuclei

Question 18

nuclide

Answer 18

any atom of any element that has a particular # of neutrons in its nucleus

Question 19

a
z X

Answer 19

a is mass number (#protons + #neutrons), z is atomic number (#protons)
*normally leave out atomic number

Question 20

protons=

Answer 20

atomic #

Question 21

neutrons =

Answer 21

mass = p + n
mass - p = n

Question 22

electrons=

Answer 22

charge changes # of protons

Question 23

7 horizontal rows called – and 18 columns called —

Answer 23

• periods
• groups/families

Question 24

elements can be broadly categorized in two ways

Answer 24

1) as main group or transition metals
2) categorizes elements as metals, nonmetals or metalloids

Question 25

all elements can form ions:

Answer 25

cations = pos. charged ions
anions = neg. charged ions

Question 26

name the groups: 1, 2, 16, 17, 18

Answer 26

1- alkali metals
2- alkaline earth metals
16- chalcogens
17- halogens
18- noble gases

Question 27

average atomic mass

Answer 27

weighted average of all isotopes of an element

Question 28

natural abundance

Answer 28

proportion of a particular isotope, relative to all the isotopes of an element

Question 29

calculating average atomic mass

Answer 29

multiple mass by abundance (/100) for each, then add all up (remember sig figs by underlining insig. digits)

Question 30

molecular mass

Answer 30

the mass of one molecule of a molecular compound **mass of whole compound
(atoms/mol x atomic mass (u/atoms) = u/mol)

Question 31

formula unit

Answer 31

the smallest electrically neutral unit of an ionic compound

Question 32

formula mass

Answer 32

mass of one formula unit of an ionic compound *mass stays same even if ion all /form unit instead of molecule (label ion as element)

Question 33

mole

Answer 33

an amount of a substance that contains a number of particles (atoms, ions, molecules) equal to avogadros constant

Question 34

avogadros constant

Answer 34

the # of atoms/ions/particles in one mole of substance (6.022 x 10^23 particles/mole) * used to cancel out atoms to find moles

Question 35

molar mass

Answer 35

g/mole, seen on the periodic table, is equal to atomic mass but expressed in g/mole

Question 36

kilo

Answer 36

10^3

Question 37

centi

Answer 37

10^-2

Question 38

nano

Answer 38

10^-9

Question 39

milli

Answer 39

10^-3

Question 40

micro

Answer 40

10^-6

Question 41

pico

Answer 41

10^-12

Question 42

to get rid of log

Answer 42

put as power of 10

Question 43

to get rid of ln

Answer 43

put as power of e

Question 44

if just log(constant) or e^(constant)

Answer 44

simplify

Question 45

sig figs

Answer 45

carry through + keep all, underline insignificant digits

Question 46

if the plum pudding model was correct, what would results of gold foil be?

Answer 46

all alpha particles would have gone through

Question 47

instead of gold foil, silver and aluminum, why might these foils of deflected fewer alpha particles?

Answer 47

smaller nuclei, odds of deflecting are lower

Question 48

proton to neutron ratio when Z increases

Answer 48

ratio also increases

Question 49

when calculation formula masses, why is the average masses of neutral atoms used not ions?

Answer 49

the mass of electrons is negligible

Question 50

finding masses of formula units

Answer 50

just find atomic mass of the whole thing

Question 51

do equal masses of two isotopes of an element contain the same number of atoms?

Answer 51

No.
g x mol/ –g (isotope #) x atoms/mol (avogadros constant)
- heavier isotopes have fewer atoms

Question 52

find the number of moles given atoms or molecules

Answer 52

divide by avogadros constant

Question 53

find moles given g

Answer 53

use molar mass