Fundamentals of
Chemistry
Lesson 1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Prof. Roberto Paolesse
Dept. of Chemical Science and Technologies
University of Rome "Tor Vergata"
Via della Ricerca Scientifica
00133 Rome, Italy
Phone: 39.06.72594752
Fax: 39.06.72594328
e-mail: roberto.paolesse@uniroma2.it
2
Textbook:
Raymond Chang:
General Chemistry: the essential concepts
6th edition ; ISBN 0071313680
McGraw-Hill Ed.
3
The Study of Chemistry
Macroscopic
Microscopic
4
The scientific method is a systematic
approach to research
A hypothesis is a tentative explanation for a
set of observations
tested
modified
5
A law is a concise statement of a relationship
between phenomena that is always the same
under the same conditions.
Force = mass x acceleration
A theory is a unifying principle that explains
a body of facts and/or those laws that are
based on them.
Atomic Theory
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Chemistry is the study of matter and the
changes it undergoes
Matter is anything that occupies space and
has mass.
A substance is a form of matter that has a
definite composition and distinct properties.
liquid nitrogen
gold ingots
silicon crystals
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A mixture is a combination of two or more substances
in which the substances retain their distinct identities.
1.  Homogenous mixture – composition of the
mixture is the same throughout.
soft drink, milk, solder
2.  Heterogeneous mixture – composition is not
uniform throughout.
cement,
iron filings in sand
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Physical means can be used to separate a mixture
into its pure components.
magnet
distillation
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An element is a substance that cannot be
separated into simpler substances by chemical
means.
•  117 elements have been identified
•  82 elements occur naturally on Earth
gold, aluminum, lead, oxygen, carbon, sulfur
•  35 elements have been created by scientists
technetium, americium, seaborgium
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A compound is a substance composed of atoms
of two or more elements chemically united in fixed
proportions.
Compounds can only be separated into their
pure components (elements) by chemical
means.
lithium fluoride
quartz
dry ice – carbon dioxide
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Classifications of Matter
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Dalton s Atomic Theory (1808)
1. Elements are composed of extremely small particles
called atoms.
2. All atoms of a given element are identical, having the
same size, mass and chemical properties. The atoms of
one element are different from the atoms of all other
elements.
3. Compounds are composed of atoms of more than one
element. In any compound, the ratio of the numbers of
atoms of any two of the elements present is either an
integer or a simple fraction.
4. A chemical reaction involves only the separation,
combination, or rearrangement of atoms; it does not
result in their creation or destruction.
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16 X
+
8Y
8 X2Y
Law of Conservation of Mass
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Cathode Ray Tube
J.J. Thomson, measured mass/charge of e(1906 Nobel Prize in Physics)
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Cathode Ray Tube
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Millikan s Experiment
Measured mass of e(1923 Nobel Prize in Physics)
e- charge = -1.60 x 10-19 C
Thomson s charge/mass of e- = -1.76 x 108 C/g
e- mass = 9.10 x 10-28 g18
Types of Radioactivity
(uranium compound)
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Thomson s Model
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Rutherford s Experiment
(1908 Nobel Prize in Chemistry)
α  particle velocity ~ 1.4 x 107 m/s
(~5% speed of light)
1.  atoms positive charge is concentrated in the nucleus
2.  proton (p) has opposite (+) charge of electron (-)
3.  mass of p is 1840 x mass of e- (1.67 x 10-24 g) 21
Rutherford s Model of
the Atom
atomic radius ~ 100 pm = 1 x 10-10 m
nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m
If the atom is the Houston Astrodome,
then the nucleus is a marble on the 50yard line.
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Chadwick s Experiment (1932)
(1935 Noble Prize in Physics)
H atoms - 1 p; He atoms - 2 p
mass He/mass H should = 2
measured mass He/mass H = 4
α + 9Be
1n
+ 12C + energy
neutron (n) is neutral (charge = 0)
n mass ~ p mass = 1.67 x 10-24 g
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mass p ≈ mass n ≈ 1840 x mass e24
Properties of Waves
Wavelength (λ) is the distance between identical points on
successive waves.
Amplitude is the vertical distance from the midline of a
wave to the peak or trough.
Frequency (ν) is the number of waves that pass through a
particular point in 1 second (Hz = 1 cycle/s).
The speed (u) of the wave = λ x ν
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Maxwell (1873), proposed that visible light consists of
electromagnetic waves.
Electromagnetic
radiation is the emission
and transmission of energy
in the form of
electromagnetic waves.
Speed of light (c) in vacuum = 3.00 x 108 m/s
All electromagnetic radiation
λ x ν = c
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Mystery #1, Heated Solids Problem
Solved by Planck in 1900
When solids are heated, they emit electromagnetic radiation
over a wide range of wavelengths.
Radiant energy emitted by an object at a certain temperature
depends on its wavelength.
Energy (light) is emitted or
absorbed in discrete units
(quantum).
E = h x ν
Planck s constant (h)
h = 6.63 x 10-34 J•s
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Mystery #2, Photoelectric Effect
Solved by Einstein in 1905
Light has both:
1.  wave nature
2.  particle nature
hν
KE e-
Photon is a particle of light
hν = KE + W
KE = hν - W
where W is the work function and
depends how strongly electrons
are held in the metal
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Line Emission Spectrum of Hydrogen Atoms
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Il modello di Bohr
Bohr s Model of
the Atom (1913)
1.  e- can only have specific
(quantized) energy
values
2.  light is emitted as emoves from one energy
level to a lower energy
level
En = -RH (
1
n2
)
n (principal quantum number) = 1,2,3,…
RH (Rydberg constant) = 2.18 x 10-18J
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E = hν
E = hν
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Ephoton = ΔE = Ef - Ei
ni = 3
ni = 3
ni = 2
nf = 2
1
Ef = -RH ( 2
nf
1
Ei = -RH ( 2
ni
1
ΔE = RH( 2
ni
)
)
1
n2f
nnf f==11
38
)
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Why is e- energy quantized?
De Broglie (1924) reasoned
that e- is both particle and
wave.
2πr = nλ
h
λ = mu
u = velocity of em = mass of e42
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Schrodinger Wave Equation
In 1926 Schrodinger wrote an equation that
described both the particle and wave nature of the eWave function (ψ) describes:
1 . energy of e- with a given ψ
2 . probability of finding e- in a volume of space
Schrodinger s equation can only be solved exactly
for the hydrogen atom. Must approximate its
solution for multi-electron systems.
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Schrodinger Wave Equation
ψ is a function of four numbers called
quantum numbers (n, l, ml, ms)
principal quantum number n
n = 1, 2, 3, 4, ….
distance of e- from the nucleus
n=1
n=2
n=3
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Where 90% of the
e- density is found
for the 1s orbital
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Schrodinger Wave Equation
quantum numbers: (n, l, ml, ms)
angular momentum quantum number l
for a given value of n, l = 0, 1, 2, 3, … n-1
n = 1, l = 0
n = 2, l = 0 or 1
n = 3, l = 0, 1, or 2
l=0
l=1
l=2
l=3
s orbital
p orbital
d orbital
f orbital
Shape of the volume of space that the e- occupies
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l = 0 (s orbitals)
l = 1 (p orbitals)
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l = 2 (d orbitals)
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Schrodinger Wave Equation
quantum numbers: (n, l, ml, ms)
magnetic quantum number ml
for a given value of l
ml = -l, …., 0, …. +l
if l = 1 (p orbital), ml = -1, 0, or 1
if l = 2 (d orbital), ml = -2, -1, 0, 1, or 2
orientation of the orbital in space
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ml = -1, 0, or 1
3 orientations is space
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ml = -2, -1, 0, 1, or 2
5 orientations is space
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Schrodinger Wave Equation
(n, l, ml, ms)
spin quantum number ms
ms = +½ or -½
ms = +½
ms = -½
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Schrodinger Wave Equation
quantum numbers: (n, l, ml, ms)
Existence (and energy) of electron in atom is described
by its unique wave function ψ.
Pauli exclusion principle - no two electrons in an atom
can have the same four quantum numbers.
Each seat is uniquely identified (E, R12, S8)
Each seat can hold only one individual at a
time
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Schrodinger Wave Equation
quantum numbers: (n, l, ml, ms)
Shell – electrons with the same value of n
Subshell – electrons with the same values of n and l
Orbital – electrons with the same values of n, l, and ml
How many electrons can an orbital hold?
If n, l, and ml are fixed, then ms = ½ or - ½
ψ = (n, l, ml, ½) or ψ = (n, l, ml, -½)
An orbital can hold 2 electrons
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How many 2p orbitals are there in an atom?
n=2
2p
If l = 1, then ml = -1, 0, or +1
3 orbitals
l=1
How many electrons can be placed in the 3d subshell?
n=3
3d
l=2
If l = 2, then ml = -2, -1, 0, +1, or +2
5 orbitals which can hold a total of 10 e60
Energy of orbitals in a single electron atom
Energy only depends on principal quantum number n
n=3
n=2
En = -RH (
1
n2
)
n=1
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Energy of orbitals in a multi-electron atom
Energy depends on n and l
n=3 l = 2
n=3 l = 0
n=2 l = 0
n=3 l = 1
n=2 l = 1
n=1 l = 0
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Fill up electrons in lowest energy orbitals (Aufbau principle)
??
B 1s22s22p1 B 5 electrons
Be 1s22s2
Be 4 electrons
Li 1s22s1
Li 3 electrons
H 1 electron He 2 electrons
He 1s2
H 1s1
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The most stable arrangement of electrons in
subshells is the one with the greatest number of
parallel spins (Hund s rule).
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Order of orbitals (filling) in multi-electron atom
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s
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Electron configuration is how the electrons are
distributed among the various atomic orbitals in an
atom.
number of electrons
in the orbital or subshell
1s1
principal quantum
number n
angular momentum
quantum number l
Orbital diagram
H
1s1
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What is the electron configuration of Mg?
Mg 12 electrons
1s < 2s < 2p < 3s < 3p < 4s
1s22s22p63s2
2 + 2 + 6 + 2 = 12 electrons
Abbreviated as [Ne]3s2
[Ne] 1s22s22p6
What are the possible quantum numbers for the last
(outermost) electron in Cl?
Cl 17 electrons
1s22s22p63s23p5
1s < 2s < 2p < 3s < 3p < 4s
2 + 2 + 6 + 2 + 5 = 17 electrons
Last electron added to 3p orbital
n=3
l=1
ml = -1, 0, or +1
ms = ½ or -½
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Outermost subshell being filled with electrons
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Paramagnetic
unpaired electrons
2p
Diamagnetic
all electrons paired
2p
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