Law of Conservation of Mass
“Francie came away from her first chemistry lecture in a glow.
In one hour she found out that everything was made up of atoms
which were in continual motion. She grasped the idea that nothing
was ever lost or destroyed. Even if something was burned up or
rot away, it did not disappear from the face of the earth; it changed
into something else - gases, liquids, and powders. Everything,
decided Francie after that first lecture, was vibrant with life and
there was no death in chemistry. She was puzzled as to why
learned people didn't adopt chemistry as a religion.”
Law of Constant Composition
“. . . The properties of true compounds are invariable as is the ratio of
their constituents. The native oxides follow the same relations of
composition as the artificial”.
“We find in the bosom of the earth copper oxide containing 20 per cent
of oxygen, arsenic with 33, lead with 9, antimony with 30, iron with 28
and 48, and others still.”
“We must conclude that nature operates not otherwise in the
depths of the world than at its surface or in the hands of man.”
J. L. Proust
A Tree Grows in Brooklyn Betty Smith, 1943
Modern Atomic Theory
Structure of the Atom?
So Horton stopped splashing. He looked towards the sound.
“That’s funny,” thought Horton. “There’s no one around.”
Then he heard it again! Just a very faint yelp
As if some tiny person were calling for help.
“I’ll help you,” said Horton. “But who are you? Where?”
He looked and he looked. He could see nothing there
But a small speck of dust blowing past though the air.
John Dalton
British
1803
1. elements made of small, indivisible particles: atoms
“I say!” murmured Horton. “I’ve never heard tell
Of a small speck of dust that is able to yell.
So you know what I think?…Why, I think that there must
Be someone on top of that small speck of dust!
Some sort of a creature of very small size,
too small to be seen by an elephant’s eyes…
2. atoms of a given element all alike (properties), but differ from atoms of
every other element in some way: mass?
...
3. compounds form when atoms of more than one element combine; a
given compound always has same relative number and kind of atom:
Law of Constant Composition
And that Yopp…
That one small, extra Yopp put it over!
Finally, at last! From that speck on that clover
Their voices were heard! They rang out clear and clean.
And the elephant smiled. “Do you see what I mean?…
They’ve proved they ARE persons, no matter how small.
4. atoms are not changed into different atoms by chemical reactions; atoms
are neither created nor destroyed: Law of Conservation of Matter
Structure of the Atom
J. J. Thomson
English
1897
e–
electron, ; fundamental particle
mass/charge ratio
Structure of the Atom
J. J. Thomson
English
1897
electron, e– ; fundamental particle
mass/charge ratio
Plum pudding atomic model
cathode-ray tube
+
+
e– “raisins”
–
–
attracted to positive: e– negatively charged
mass
= –5.68 x 10–9 g/C (from deflection)
charge
+ charged
“pudding”
1
Structure of the Atom
Thomson on the size of the electron
electron, e– ; fundamental particle
mass/charge ratio
plum pudding atomic model
J. J. Thomson
English
1897
Robert Millikan
American
1909
oil drop experiment
charge on e– : –1.602 x 10–19 C
+
atomizer
oil drops
–
X-rays
"Could anything at first sight seem more
impractical than a body which is so small
that its mass is an insignificant fraction of
the mass of an atom of hydrogen? --which
itself is so small that a crowd of these
atoms equal in number to the population of
the whole world would be too small to have
been detected by any means then known to
science."
microscope
–
Rutherford’s Experiment
Structure of the Atom
electron, e– ; fundamental particle
mass/charge ratio
plum pudding atomic model
J. J. Thomson
English
1897
gold-foil experiment: a particle probes Ernest Rutherford
New Zealand
planetary atomic model
1908 - 1911
Pb box with a2+ source
(RaCl2)
fluorescent detector
(ZnS)
Robert Millikan
American
1909
oil drop experiment
charge on e– : –1.602 x 10–19 C
mass of
Henri Becquerel
e– :
Marie and Pierre Curie
French
1895 - 1903
9.109 x
10–28
g
few atoms thick
Au foil
Expected results:
radioactivity
a particles: He2+
b particles: e–
g radiation: X-rays
Au atom
Rutherford’s Experiment
gold-foil experiment: a particle probes Ernest Rutherford
New Zealand
planetary atomic model
1908 - 1911
Structure of the Atom
gold-foil experiment: a particle probes Ernest Rutherford
New Zealand
planetary atomic model
1908 - 1911
most went directly through; but a few reflected back!
atomic number (Z) (using X-rays)
interpretation:
“…integers (on periodic table) are
characteristic of the elements [and]
the same as # of electrical units
[+ charges] in the nucleus.”
“It was about as credible as if you had fired a 15-inch shell at a
piece of tissue paper and it came back and hit you.”
Henry Moseley
English
1913
Atomic Number
planetary model
Emitted X-rays Wavelength
2
Structure of the Atom
discovered the proton:
N2 + a
p+
O2 +
Structure of Neutral Atom
e–
Ernest Rutherford
New Zealand
1908 - 1911
orbiting small, dense nucleus: p+ + n0
atomic number
Z = # p+
(Ger zahl “number”)
identity of atom
1836 x heavier than e– (1.67252 x 10–24 g)
James Chadwick
English
1932
discovered the neutron:
Be + a
n0
C +
slightly larger than
p+
(1.67495 x
10–24
# e– = # p+
neutral atom
10–5
1
g)
particle
charge
relative mass
p+
+
1.0000
n0
0
1.0014
e–
–
5.446 x 10–4
mass number
A = # p+ + # n0
atomgewicht
related to PT mass
A
Z
X
Evidence of Atoms
element name – A
6
3
lithium – 6
Li
Metals, Nonmetals, Metalloids
Atomic Force Microscope
nonmetals He
H
B C N O F Ne
Li Be
metals
Na Mg
Al Si P
S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
I Xe
Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Lr Rf Db Sg Bh Hs Mt Ds Rg Cn
Fl
Lv
metalloids or semi-metals
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No
Periodic Table Families
H
Compounds
He
Li Be
B C N O F Ne
Na Mg
Al Si P
S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
Hg
+
S
C
+
S
I Xe
Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Lr Rf Db Sg Bh Hs Mt Ds Rg Cn
Fl
Lv
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No
Li alkali metals
N
pnictogens
He noble gases
Be alkaline-earth metals
O
chalcogens
La lanthanides
Sc transition metals
F
halogens
Ac actinides
cinnabar
Svante Arrhenius
Swedish
carbon disulfide
1884
3
Ionic
Ion Charges from Periodic Table
(Gr: mobile)
collections of oppositely charged particles: ions
formed from atoms or groups of atoms by
losing e– or gaining e–
cation (+) anion (–)
(e– < p+)
(e– > p+)
#+, #–
1+, 1–  +, –
Na+
11 p+
10 e–
Mg2+
12 p+
10 e–
X
2+
Li
S Cl
Se Br
Cl–
17 p+
18 e–
nonmetal ion
name –ide suffix
Ra
empirical formula: cation anion; +/– in a ratio that adds to 0:
hydride, carbide, nitride, oxide, fluoride, phosphide,
sulfide, chloride, selenide, bromide, iodide
magnitude of charge given first, followed by + or –
1+ and 1– given as + and –
all other metal ions have
variable charges
1+, 2+, 3+, 4+, etc ?
Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga
Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn
Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po
Fl
I
Cs Ba
Non-predictable Charges on Monatomic Cations
Lv
name includes charge in (Roman numerals):
Fe3+ iron(III)
Cu2+ copper(II)
Sn4+ tin(IV)
P
Al
Rb Sr
very different from neutral atom
Fe2+ iron(II)
Cu+ copper(I)
Sn2+ tin(II)
Hg2+ mercury(II)
C N O F
metal ion
K Ca
F–
19 p+
10 e–
Lr Rf Db Sg Bh Hs Mt Ds Rg Cn
3+(4–) 3– 2– 1–
Na Mg name as element
n– (n = # e– gained)
n+ (n = # e– lost)
O2–
18 p+
10 e–
H
1+
Fe4+ iron(IV)
Cu3+ copper(III)
Ionic: Recognize, Formula and Name
1. binary: 2 atom types: metal + nonmetal
a. metal ion name as element (predictable)
or element + (Roman numeral) charge (not)
b. modify nonmetal ion element name: –ide
H
carbide, nitride, oxide, fluoride, phosphide,
1+
sulfide, chloride, selenide,
3+ C N O F
Li 2+
bromide, iodide, hydride
Al 4– P
Na Mg
S Cl
3– Se Br
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn
2– I
Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi
Ra Lr Rf Db Sg Bh Hs Mt Ds Rg Cn
Fl
1–
Lv
2. >2 atom types: polyatomic ions; formula, name and charge
Polyatomic Anions
1–
2–
3–
–ate, –ite
NO3–
nitrate
SO42–
sulfate
PO43–
phosphate
NO2–
nitrite
SO32–
sulfite
PO33–
phosphite
HSO4 – hydrogen sulfate
Polyatomic Cations
ClO–
hypochlorite (hypo-, fewer)
ClO2– chlorite
NH4+
ammonium
(also
Br,
I)
ClO3– chlorate
Hg22+
mercury(I)
ClO4– perchlorate (per-, most)
mercurous
no –ite
C2H3O2– acetate
CO32–
carbonate
C2O42– oxalate
M containing
MnO4– permanganate CrO42– chromate
Cr2O72– dichromate (di-, 2)
polyatomic –ide
N 3–
azide
O22–
peroxide
OH–
hydroxide
–
CN
cyanide
Ionic: Naming, Recognizing, and Formula
CuSO4
Cu2+
SO42–
4
Molecular
Ionic: Formula and Name
Ba
F
binary: 2 atom types
recognize: all nonmetals
 Na3N
aluminum sulfide
Cu+
Sn2+
O
P
 2 atoms, uncharged, act as a unit:
H2O
formula cannot be predicted from the elements
 FeCl2
some elements are molecular
H H2
iron(III) chloride
N2 O 2
Cu2+ SO42–
Ni2+ CrO42–
B C N O F
Si P
Ga2(CO3)3
F2
S Cl Cl2
Se Br Br2
magnesium nitrate
I
I2
NH4+ PO33–
Molecular: Formula and Naming
B C N O F
formula: most metallic then most nonmetallic
Si P S Cl
hydrogen peroxide Se Br
I
empirical:
molecular:
structural:
smallest ratio
HO
exact number
H2O2
shows connectivity H–O–O–H
first atom named as a cation (it’s not);
second as an anion (it’s not);
# of each atom with prefix
name:
mono
penta
nona
1 di
5 hexa
9 deca
2 tri
3 tetra
4
6 hepta
7 octa
8
10 undeca 11 dodeca 12
Molecular: Recognizing, Formula, and Naming
NCl3
P2O5

boron trihydride

tetraphosphorus trisulfide

dinitrogen tetroxide
CO
S2Br2
OF2
N2O
NO
N2O3
NO2
N2O5
Other Naming
hydrates
ionic with specific # attached H2O
“dot”
formula

#H2O name prefixhydrate
CuSO4  5H2O copper(II) sulfate pentahydrate
acids
recognize:
name:
anion
–ide
–ate
–ite
contains H+, given first
from anion
acid
hydro–ic CN– cyanide
SO42– sulfate
–ic
–ous
ClO2– chlorite
HCN
hydrocyanic acid
H2SO4 sulfuric acid
HClO2 chlorous acid
5