Download Atoms and Elements - Melvin R. Kantz, Ph.D.

Atoms and
Elements
John Dalton
1766-1844
Dalton developed the atomic
theory of matter as a
consequence of his researches
on the behaviour of gases. He
developed the laws of definite
and multiple proportions. A
complete scientist, Dalton also
made important observations on
the aurora borealis, rain, trade
winds, and color blindness. The
atomic mass unit, the Dalton, is
named for him.
MSU Gallery of Chemists' Photo-Portraits and MiniBiographies
http://poohbah.cem.msu.edu/Portraits
Scanning Tunneling Microscope
1986 Nobel Prize
Operation of a STM
Superconducting YBa2Cu3O7
Early Philosophy of Matter
• ultimate, tiny, indivisible particle
Leucippus and Democritus
• infinitely divisible
Plato and Aristotle
• best debater was the person assumed correct,
i.e., Aristotle
Scientific Revolution
• late 16th century, the scientific approach to
understanding nature
• next 150+ years, observations about nature were
made that could not easily be explained
Aristotelian approach
Law of Conservation of Mass
total m reactants = total m of products
Antoine Lavoisier
1743-1794
Reaction of Sodium with Chlorine to
Make Sodium Chloride
7.7 g Na
+ 11.9 g Cl2
19.6 g NaCl
LAW OF DEFINITE PROPORTIONS
All samples of a given
compound, regardless of
their source or how they
were prepared, have the
___________________
___________________

Joseph Proust
1754-1826
Proportions in Sodium Chloride
a 100.0 g sample of sodium
mass of Cl 60.7 g
1.54
chloride contains 39.3 g of sodium
mass of Na 39.3 g
and 60.7 g of chlorine
a 200.0 g sample of sodium
mass of Cl 121.4 g
1.54
chloride contains 78.6 g of sodium
mass of Na 78.6 g
and 121.4 g of chlorine
a 58.44 g sample of sodium
mass of Cl 35.44 g
1.541
chloride contains 22.99 g of sodium
mass of Na 22.99 g
and 35.44 g of chlorine
LAW OF MULTIPLE PROPORTIONS

When two elements A
and B form two
different compounds,
the masses of B that
combine with 1 g of A
can be expressed as
a _________________
John Dalton
1766-1844
Oxides of Carbon
• carbon monoxide contains 1.33 g of
•
•
oxygen for every 1.00 g of carbon
carbon dioxide contains 2.67 g of
oxygen for every 1.00 g of carbon
since there are twice as many oxygen
atoms per carbon atom in carbon
dioxide than in carbon monoxide, the
oxygen mass ratio should be 2
mass of oxygen that combines with 1 g of carbon in carbon dioxide
mass of oxygen that combines with 1 g of carbon in carbon monoxide
2.67 g
1.33 g
2
DALTON’S ATOMIC THEORY
1)
2)
3)
4)
Each element is composed of tiny, indestructible
particles called atoms …still correct?
All atoms of a given element has the same mass
and other properties that distinguish them from
atoms of other elements…still correct?
Atoms combine in simple, whole-number ratios to
form molecules of compounds
In a chemical reaction, atoms of one element
cannot change into atoms of another element

they simply rearrange the way they are attached
Some Notes on Charge
Cathode Ray Tubes
anode
cathode
J.J. THOMSON

cathode ray was composed of tiny particles
with an electrical charge

measured the amount of _____ it takes to
deflect their path a given amount
Thomson’s Experiment
THOMSON’S RESULTS


the cathode rays are made of tiny particles
these particles have a ____________charge




because the beam always deflected toward the + plate
the amount of deflection was related to two
factors______________ and ______________
every material tested contained these same particles
the charge/mass of these particles was -1.76 x 108
C/g

the charge/mass of the hydrogen ion is +9.58 x 104 C/g
THOMSON’S CONCLUSIONS

if the particle has the same amount of charge as a
hydrogen ion, then it must have a mass almost
2000x smaller than hydrogen atoms!


the only way for this to be true is if these particles
were pieces of atoms



later experiments by Millikan showed that the particle did
have the same amount of charge as the hydrogen ion
apparently, the atom is not unbreakable
Thomson believed that these particles were
therefore the ultimate building blocks of matter
these cathode ray particles became known as
________
Millikan’s Oil Drop Experiment
Electrons
•
•
•
•
electrons are particles found in all atoms
cathode rays are streams of electrons
the electron has a charge of -1.60 x 1019 C
the electron has a mass of 9.1 x 10-28 g
A New Theory of the Atom
Thomson’s Plum Pudding Atom
or maybe a raisins in oatmeal model
Predictions of the Plum Pudding Atom
• the mass of the atom is due to the mass of the
electrons within it
electrons are the only particles in Plum Pudding
atoms
• the atom is mostly empty space
cannot have a bunch of negatively charged particles
near each other as they would repel
RADIOACTIVITY



in the late 1800s, Henri Becquerel and Marie Curie
certain elements emit small, energetic particles or rays
these energetic particles could penetrate matter
Ernest Rutherford discovered that there were three
different kinds of emissions



____________particles with a mass 4x H atom and + charge
_______particles with a mass ~1/2000th H atom and – charge
_______________that are energy rays, not particles
Rutherford’s Experiment
How can you prove something is empty?
Rutherford’s Experiment
Alpha Particles
Striking Screen
Radioactive
Sample
Lead Box
Gold
Foil
Fluorescent
Screen
Rutherford’s Results
• Over 98% of the particles went straight
through
• About 2% of the particles went through
but were deflected by large angles
• About 0.01% of the particles bounced off
the gold foil
“...as if you fired a 15” cannon shell at a piece
of tissue paper and it came back and hit you.”
RUTHERFORD’S CONCLUSIONS

Atom mostly _______________________


Atom contains a dense ______ that was small in
volume compared to the atom but large in mass


because almost all the particles went straight through
because ________________________________
This dense particle was __________ charged

because of the large ______________ of some of the
particles
Plum Pudding
Atom
•
•
•
•
•
•
•
•
•
•
a few of the
particles
do not go through
•
•
•
•
•
•
•
•
•
•
•
•
if atom was like
a plum pudding,
all the particles
should go
straight through
Nuclear Atom
.
.
most particles
go straight through
.
some particles
go through, but are deflected
RUTHERFORD’S INTERPRETATION –
THE NUCLEAR MODEL
1)
The atom contains a tiny dense center called the
______________________

2)
The _______ has essentially the entire ____ of the
atom

3)
the _______ weigh so little they give practically no mass
to the atom
The ______ is _________ charged

4)
the amount of space taken by the ________ is only about
1/10 trillionth the volume of the atom
the amount of positive charge balances the negative
charge of the electrons
The electrons are dispersed in the empty space of
the atom surrounding the nucleus
STRUCTURE OF THE ATOM

same amount of charge as an
electron but opposite sign
 based
on measurements of the nuclear
charge of the elements

protons
 charge
= +1.60 x 1019 C
 mass = 1.67262 x 10-24 g

For an atom to be neutral there must
be equal
________________________
Relative Mass and Charge
• we generally talk about the mass of atoms by
comparing it to 1/12th the mass of a carbon atom
with 6 protons and 6 neutrons, which we call 1
atomic mass unit
protons have a mass of 1amu
electrons have a mass of 0.00055 amu,
Some Problems
• How could beryllium have 4 protons stuck
together in the nucleus?
• If a beryllium atom has 4 protons, then it
should weigh 4 amu; but it actually weighs
9.01 amu! Where is the extra mass coming
from?
each proton weighs 1 amu and the mass of the
electrons is trivial
THERE MUST BE SOMETHING ELSE THERE!
to answer these questions, Rutherford
proposed that there was another particle in
the nucleus – it is called a _____________
 ______ have no charge and a mass of 1
amu

 mass
= 1.67493 x 10-24 g
 slightly
 no
heavier than a proton
charge
ELEMENTS
each element has a unique number of protons
in its nucleus
 the number of protons in the nucleus of an
atom is called the _______________= Z



the elements are arranged on the current Periodic
Table in order of their __________________
each element has a unique name and symbol

symbol either one or two letters
 one
capital letter or one capital letter + one lowercase
STRUCTURE OF THE NUCLEUS

Soddy discovered that the same element
could have atoms with different masses,
which he called _______________
 there
are 2 ___________of chlorine found in
nature, one that has a mass of about 35 amu
and another that weighs about 37 amu

The observed mass is a weighted average of
the weights of all the naturally occurring
atoms
 the
percentage of an element that is 1 _____ is
called the isotope’s natural abundance
 the atomic mass of chlorine is 35.45 amu

all ______ of an element are chemically
identical
 undergo
the same chemical reactions
all _______ of an element have the same
number of protons
 ________ of an element have different masses
 ______ of an element have different numbers of
neutrons
• ________ are identified by their integer ______number

= # protons + # neutrons
Mass Spectrometer
Mass Spectrometer
Mass Spectrum Result
• a mass__________is a graph
•
•
that gives the relative mass
and relative abundance of
each particle
relative mass of the particle is
plotted in the x-axis
relative abundance of the
particle is plotted in the yaxis
ATOMIC MASS

we previously learned that not all atoms of an
element have the same mass


we generally use the average mass of all an
element’s atoms found in a sample in calculations


isotopes
however the average must take into account the
abundance of each isotope in the sample
we call the average mass the __________________
Atomic Mass
fractional abundance of isotope
n
mass of isotope
n
NEON
Example 2.5 If copper is 69.17% Cu-63 with a mass of 62.9396 amu and
the rest Cu-65 with a mass of 64.9278 amu, find copper’s atomic mass
Given:
Find:
Concept Plan:
Cu-63 = 69.17%, 62.9396 amu
Cu-65 = 100-69.17%, 64.9278 amu
atomic mass, amu
Relationships:
Atomic Mass
Solution:
isotope masses,
isotope fractions
avg. atomic mass
fractional abundance of isotope
Atomic Mass
n
mass of isotope
0.6917 62.9396 amu
0.3083 64.9278 amu
Atomic Mass 63.5525 63.55 amu
Check:
the average is between the two masses,
closer to the major isotope
n
CHARGED ATOMS
Ions
+ Ions Called______________
Originate from _________
- Ions Called______________
Originate from _________
ATOMIC STRUCTURES OF IONS

Anions are named by changing the ending of
the name to -_____________
fluorine F + 1e- F─ _________________
oxygen
O + 2e- O2─ ___________
ATOMIC STRUCTURES OF IONS

Cations are named ___________________
sodium
calcium
Na
Ca
Na+ + 1eCa2+ + 2e-
_________
__________
D.MENDELEEV (1870) AND
H.MOSLEY (1914)

_________ Law – When the elements are arranged
in order of increasing atomic (mass) number,
certain sets of properties recur periodically
Periodic Pattern
nm H2O
a/b
H
1
H2
m Li2O m/nm BeOnm B2O3 nm CO2 nm N2O5 nm
O2 nm
Li b
Be a/b B a
C a N a
O
F
7 LiH 9 BeH2 11 ( BH3)n 12 CH4 14 NH3 16 H2O 19 HF
m Na2O m MgO m Al2O3 nm/m SiO2nm P4O10nm SO3 nm Cl2O7
Na b Mg b Al a/b Si a P a
S a Cl a
23 NaH24 MgH2 27 (AlH3) 28 SiH4 31 PH3 32 H2S 35.5 HCl
m = metal, nm = nonmetal, m/nm = metalloid
a = acidic oxide, b = basic oxide, a/b = amphoteric oxide
Mendeleev’s Periodic Chart
1871
Mendeleev’s Predictions for Ekasilicon (Germanium)
Property
Atomic
Mass
Color
Silicon’s
Props
28
Tin’s
Props
118
Grey
Grey
5.5
GreyWhite
5.4
Resists
Both
Resists
Both
Eks1O2
GeO2
Density
2.32
White
metal
7.28
Reaction
w/ Acid &
Base
Resists
Acid,
Reacts
Base
SiO2
Reacts
Acid,
Resists
Base
SnO2
Oxide
Predicted Measured
Value
Value
72
72.6
METALS
List typical or descriptive properties
 __________________________________
 __________________________________
 __________________________________
 __________________________________
 __________________________________
Give the operational definition of a metal:
________________________________
________________________________
NONMETALS ARE FOUND
IN ALL 3 ______________
Sulfur, S(s)
List typical or descriptive properties








_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
Give the operational definition of a
nonmetal:
________________________________
________________________________
Bromine, Br2(l)
Chlorine, Cl2(l)
METALLOIDS
show some
properties of
metals and some
of nonmetals
 also known as
_______conductors

Properties of Silicon
shiny
conducts electricity
poorly
does not conduct heat
well
brittle
Patterns in Metallic Character
= Metal
= Metalloid
= Nonmetal
THE MODERN PERIODIC TABLE
Elements with similar chemical and
physical properties are in the __________
 _________ are called Groups or Families

 designated
by a number and letter at top
rows are called _______________
 each ______ shows the pattern of
properties repeated in the next period

The Modern Periodic Table
• Main Group = Representative Elements = “A”
groups
• Transition Elements = “B” groups
all metals
• Bottom Rows = Inner Transition Elements =
Rare Earth Elements
metals
really belong in Period 6 & 7
= Alkali Metals
= Halogens
= Alkali Earth Metals
= Lanthanides
= Noble Gases
= Actinides
= Transition Metals
Important Groups - Hydrogen
• nonmetal
• colorless, diatomic gas
 very low melting point and density
• reacts with nonmetals to form molecular
compounds
 HCl is acidic gas
 H2O is a liquid
• reacts with metals to form hydrides
 metal hydrides react with water to form H2
• HX dissolves in water to form acids
Important Groups - Alkali Metals
• Group IA = Alkali Metals
• soft, low melting points, low density
lithium
• flame tests
• very reactive
• water-soluble compounds,
colorless
sodium
potassium
rubidium
• react with water to form basic
(alkaline) solutions and H2
2 Na + 2 H2O 2 NaOH + H2
releases a lot of heat
cesium
Important Groups - Alkali Earth Metals
• Group IIA = Alkali Earth Metals
• harder, higher melting, and denser
•
than alkali metals
 Mg alloys used as structural
materials
flame tests
beryllium
magnesium
• reactive
calcium
• form stable, insoluble oxides from
strontium
•
•
which they are normally extracted
oxides are basic
barium
reactivity with water to form H2
Be = none; Mg = steam; Ca, Sr, Ba =
cold water
Important Groups - Halogens
• Group VIIA = Halogens
• nonmetals
fluorine
• all diatomic
chlorine
• very reactive
• Cl2, Br2 react slowly with water
bromine
Br2 + H2O
HBr + HOBr
• react with metals to form ionic
•
compounds
HX all acids
 HF weak < HCl < HBr < HI
iodine
astatine
Important Groups - Noble Gases
• Group VIIIA = Noble Gases
• all gases
 very low melting and boiling
points
helium
neon
• very unreactive, practically
•
•
inert
BECAUSE IT IS
very hard to remove electron
from or give an electron to
argon
krypton
xenon
ION CHARGE AND THE PERIODIC
TABLE
the charge on an ion of a representative
element can often be determined from an
element’s position on the Periodic Table
 metals _________________
 Nonmetals_____________________
 main group metals, Charge = _______
 nonmetals, charge = ________________

1A
2A
3A
Li+1
Na+1 Mg+2
Al+3
5A 6A 7A
N-3 O-2
F-1
S-2
Cl-1
K+1 Ca+2
Se-2 Br-1
Rb+1 Sr+2
Te-2 I-1
Cs+1 Ba+2
The Mole
Counting Atoms by Moles
WHY?
•
The number of atoms we will use is 6.022 x 1023
and we call this a mole
 1 mole = 6.022 x 1023 things
 Like 1 dozen = 12 things
Chemical Packages - Moles
•
mole = number of particles equal to the
number of atoms in 12 g of C-12
 1 atom of C-12 weighs exactly 12 amu
 1 mole of C-12 weighs exactly 12 g
•
The number of particles in 1 mole is called
Avogadro’s Number = 6.0221421 x 1023
 1 mole of C atoms weighs 12.01 g and has
6.022 x 1023 atoms
 the average mass of a C atom is 12.01 amu
Example 2.6 Calculate the number of atoms
in 2.45 mol of copper
Given:
Find:
Concept Plan:
2.45 mol Cu
atoms Cu
mol Cu
atoms Cu
6.022 10 23 atoms
1 mol
Relationships:
Solution:
1 mol = 6.022 x 1023 atoms
6.022 1023 atoms
2.45 mol Cu
1 mol
1.48 1024 atoms Cu
Check:
since atoms are small, the large number of atoms
makes sense
RELATIONSHIP BETWEEN
MOLES AND MASS
The mass of one mole of atoms is called the
_____________
Mole and Mass Relationships
hydrogen
carbon
Weight of
Pieces in
1 atom
1 mole
1.008 amu 6.022 x 1023 atoms
12.01 amu 6.022 x 1023 atoms
Weight of
1 mole
1.008 g
12.01 g
oxygen
16.00 amu 6.022 x 1023 atoms
16.00 g
sulfur
32.06 amu 6.022 x 1023 atoms
32.06 g
calcium
40.08 amu 6.022 x 1023 atoms
40.08 g
chlorine
35.45 amu 6.022 x 1023 atoms
35.45 g
copper
63.55 amu 6.022 x 1023 atoms
63.55 g
Substance
1 mole
sulfur
32.06 g
1 mole
carbon
12.01 g
Example 2.7 Calculate the moles of carbon
in 0.0265 g of pencil lead
Given:
Find:
Concept Plan:
0.0265 g C
mol C
gC
mol C
1 mol
12.01 g
Relationships: 1 mol C = 12.01 g
Solution:
1 mol
0.0265 g C
12.01 g
2.21 10-3 mol C
Check:
since the given amount is much less than 1 mol C,
the number makes sense
Example 2.8 How many copper atoms are in
a penny weighing 3.10 g?
Given:
Find:
Concept Plan:
Relationships:
Solution:
Check:
3.10 g Cu
atoms Cu
g Cu
1 mol
63.55 g
1 mol Cu = 63.55 g,
1 mol = 6.022 x 1023
mol Cu
atoms Cu
6.022 10 23 atoms
1 mol
1 mol Cu 6.022 10 23 atoms
3.10 g Cu
63.55 g Cu
1 mol
2.94 10 22 atoms Cu
since the given amount is much less than 1 mol Cu,
the number makes sense
What element is defined by the following information?
•
•
•
•
•
p+ = 11 n° = 12 e- = 11
A) sodium
B) vanadium
C) magnesium
D) titanium
•
•
•
•
•
•
p+ = 11 n° = 12 e- = 11
A) sodium
B) vanadium
C) magnesium
D) titanium
Answer: A
What element is defined by the following information?
p+ = 17 n° = 20 e- = 17
• A) calcium
• B) rubidium
• C) chlorine
• D) neon
• E) oxygen
p+ = 17 n° = 20 e- = 17
• A) calcium
• B) rubidium
• C) chlorine
• D) neon
• E) oxygen
• Answer: C
What does X represent in the symbol?
80 X
35
•
•
•
•
•
A) mercury
B) chlorine
C) scandium
D) bromine
E) selenium
•
•
•
•
•
•
A) mercury
B) chlorine
C) scandium
D) bromine
E) selenium
Answer: D
Determine the number of protons, neutrons and
electrons in :
•
•
•
•
•
•
40 X
18
A) p+ = 18 n° = 18 e- = 22
B) p+ = 18 n° = 22 e- = 18
C) p+ = 22 n° = 18 e- = 18
D) p+ = 18 n° = 22 e- = 40
E) p+ = 40 n° = 22 e- = 18
Answer: B
A) p+ = 18 n° = 18 e- = 22
B) p+ = 18 n° = 22 e- = 18
C) p+ = 22 n° = 18 e- = 18
D) p+ = 18 n° = 22 e- = 40
E) p+ = 40 n° = 22 e- = 18
Answer: B
What species is represented by the
following information?
•
•
•
•
•
•
p+ = 12 n° = 14 e- = 10
A) Si4+
B) Mg
C) Ne
D) Si
E) Mg2+
p+ = 12 n° = 14 e- = 10
A) Si4+
B) Mg
C) Ne
D) Si
E) Mg2+
Answer: E
What species is represented by the
following information?
•
•
•
•
•
•
p+ = 17 n° = 18 e- = 18
A) Cl
B) ClC) Ar
D) Ar+
E) Kr
p+ = 17 n° = 18 e- = 18
A) Cl
B) ClC) Ar
D) Ar+
E) Kr
Answer: B
Which of the following elements is a
metal?
•
•
•
•
•
A) As
B) C
C) I
D) Sn
E) Se
A) As
B) C
C) I
D) Sn
E) Se
Answer: D
Which of the following elements is a
halogen?
•
•
•
•
•
•
A) Ne
B) I
C) O
D) Mg
E) K
Answer: B
A) Ne
B) I
C) O
D) Mg
E) K
Answer: B
Predict the charge that an aluminum ion
would have.
•
•
•
•
•
A) 5B) 1+
C) 1D) 2+
E) 3+
A) 5B) 1+
C) 1D) 2+
E) 3+
Answer: E
Two samples of potassium iodide are decomposed into
their constituent elements. The first sample produced 13.0
g of potassium and 42.3 g of iodine. If the second sample
produced 24.4 kg of potassium, how many kg of iodine
were produced?
• A) 13.3 kg
•
•
•
•
B) 22.5 kg
C) 79.4 kg
D) 44.4 kg
E) 92.4 kg
A) 13.3 kg
B) 22.5 kg
C) 79.4 kg
D) 44.4 kg
E) 92.4 kg
Answer: C
Calculate the atomic mass of silver if silver has 2
naturally occurring isotopes with the following masses
andatural abundances:
Ag-107 106.90509 amu 51.84%
Ag-109 108.90476 amu 48.46%
• A) 107.90 amu
• B) 108.00 amu
• C) 107.79 amu
• D) 108.32 amu
• E) 108.19 amu
A) 107.90 amu
B) 108.00 amu
C) 107.79 amu
D) 108.32 amu
E) 108.19 amu
Answer: E
How many xenon atoms are contained
in 2.36 moles of xenon?
•
•
•
•
•
•
A) 3.92 × 1024 xenon atoms
B) 2.55 × 1023 xenon atoms
C) 1.42 × 1024 xenon atoms
D) 7.91 × 1025 xenon atoms
E) 1.87 × 1026 xenon atoms
Answer: C
A) 3.92 × 1024 xenon atoms
B) 2.55 × 1023 xenon atoms
C) 1.42 × 1024 xenon atoms
D) 7.91 × 1025 xenon atoms
E) 1.87 × 1026 xenon atoms
Answer: C
What mass (in mg) does 2.63 moles of nickel have?
•
•
•
•
•
A) 44.8 mg
B) 2.23 × 104 mg
C) 129 mg
D) 3.56 x 105 mg
E) 1.54 x 105 mg
A) 44.8 mg
B) 2.23 × 104 mg
C) 129 mg
D) 3.56 x 105 mg
E) 1.54 x 105 mg
Answer: E
How many moles of Cs are contained in 595 kg of Cs?
•
•
•
•
•
A) 2.23 × 102 moles Cs
B) 4.48 × 103 moles Cs
C) 7.91 × 104 moles Cs
D) 1.26 × 103 moles Cs
E) 5.39 × 102 moles Cs
A) 2.23 × 102 moles Cs
B) 4.48 × 103 moles Cs
C) 7.91 × 104 moles Cs
D) 1.26 × 103 moles Cs
E) 5.39 × 102 moles Cs
Answer: B