Ernest Rutherford (1871-1937)

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Ernest Rutherford (1871-1937)

• Won the Nobel Prize in Chemistry in 1908
• It was quite the most incredible event..... It
  was almost as if a gunner were to fire a shell at
  a piece of tissue and the shell bounced right
  back!!!!!

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Figure 2.7 Alpha-particle scattering from metal
foils.
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Figure 2.8 Representation of the scattering of
alpha particles by a gold foil.
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Fig. 2.13
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Figure 2.9 A representation of two isotopes of
carbon.
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Atomic Definitions I Symbols, Isotopes,Numbers
A
X
The Nuclear Symbol of the Atom, or Isotope
Z
X Atomic symbol of the element, or element
symbol
A The Mass number A Z N Z The Atomic
Number, the Number of Protons in the Nucleus N
The Number of Neutrons in the Nucleus
Isotopes atoms of an element with the same
number of protons, but
different numbers of Neutrons in the Nucleus
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Depicting the Atom
Fig. 2.14
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Neutral ATOMS

• 51 Cr P (24), e- (24),
• N (27)
• 239 Pu P(94), e- (94),
• N (145)
• 15 N P(7), e-(7), N(8)
• 56 Fe P(26), e-(26),
• N (50)
• 235 U P(92), e-(92),
• N (143)

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Isotopes of Hydrogen

• 11H 1 Proton 0 Neutrons 99.985
  1.00782503 amu
• 21H (D) 1 Proton 1 Neutron 0.015
  2.01410178 amu
• 31H (T) 1 Proton 2 Neutrons
  -------- ----------
• The average mass of
  Hydrogen is 1.008 amu
• 3H is Radioactive with a half life of 12 years.
• H2O Normal water light water
• mass 18.0 amu , BP 100.000000C
• D2O Heavy water
• mass 20.0 amu , BP 101.42 0C

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Element 8 Oxygen, Isotopes

• 168O 8 Protons 8
  Neutrons
• 99.759 15.99491462
  amu
• 178O 8 Protons 9
  Neutrons
• 0.037
  16.9997341 amu
• 188O 8 Protons 10
  Neutrons
• 0.204
  17.999160 amu

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Calculating the Average Atomic Mass of an
Element
Problem Calculate the average atomic mass of
Magnesium! Magnesium Has three
stable isotopes, 24Mg ( 78.7)
25Mg (10.2) 26Mg (11.1).
24Mg (78.7) 23.98504 amu x 0.787
18.876226 amu 25Mg (10.2) 24.98584
amu x 0.102 2.548556 amu 26Mg (11.1)
25.98636 amu x 0.111 2.884486 amu

24.309268 amu
With Significant Digits 24.3 amu
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Problem Calculate the abundance of the two
Bromine isotopes 79Br 78.918336 g/mol
and 81Br 80.91629 g/mol , given that
the average mass of Bromine is 79.904 g/mol.
Plan Let the abundance of 79Br X and of 81Br
Y and X Y 1.0
Solution X(78.918336) Y(80.91629)
79.904 X Y 1.00 therefore X
1.00 - Y (1.00 - Y)(78.918336)
Y(80.91629) 79.904 78.918336 -
78.918336 Y 80.91629 Y 79.904 1.997954 Y
0.985664 or Y 0.4933 X 1.00 -
Y 1.00 - 0.4933 0.5067 X
79Br 0.5067 x 100 50.67 79Br
Y 81Br 0.4933 x 100 49.33 81Br
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Modern Reassessment of the Atomic Theory
1. All matter is composed of atoms. Although
atoms are composed of smaller particles
(electrons, protons, and neutrons), the atom
is the smallest body that retains the unique
identity of the element. 2. Atoms of one element
cannot be converted into atoms of another
element in a chemical reaction. Elements can only
be converted into other elements in Nuclear
reactions in which protons are changed. 3. All
atoms of an element have the same number of
protons and electrons, which determines the
chemical behavior of the element. Isotopes
of an element differ in the number of neutrons,
and thus in mass number, but a sample of the
element is treated as though its atoms have
an average mass. 4. Compounds are formed by the
chemical combination of two or more elements
in specific ratios, as originally stated by
Dalton.
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Definitions

• ELEMENT - A substance that cannot be separated
  into simpler substances by chemical means
• COMPOUND - A substance composed of atoms of two
  or more elements chemically united in fixed
  proportions
• PERIODIC TABLE - MENDELEEV TABLE - A tabular
  arrangement of the elements, vertical groups or
  families of elements based upon their chemical
  properties - actually combining ratios with
  oxygen

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Fig. 2.16
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Fig. 2.17
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The Periodic Table of the Elements
Most Probable Oxidation State
1
0
2
3
_4
- 3
- 2
- 1
H
He
Li
Be
B
C
F
O
N
Ne
3
4
Na
Mg
Al
Si
Cl
S
P
2
1
5
Ar
K
Sc
Ca
Ga
Ti
Ge
Br
Se
As
Zn
Cu
V
Kr
Cr
Mn
Fe
Co
Ni
Rb
Sr
Zr
I
Ag
Nb
Xe
Mo
Tc
Ru
Rh
Pd
Y
In
Sn
Te
Sb
Cd
Ba
Hg
Au
Rn
W
Re
Os
Ir
Pt
Cs
La
Tl
Hf
Pb
At
Po
Bi
Ta
Fr
Ra
Ac
Rf
Du
Sg
Bo
Ha
Me
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
3
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
3
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Groups in the Periodic Table
Main Group Elements (Vertical Groups) Group
IA - Alkali Metals Group IIA - Alkaline Earth
Metals Group IIIA - Boron Family Group
IVA - Carbon Family Group VA - Nitrogen
Family Group VIA - Oxygen Family (Calcogens)
Group VIIA - Halogens Group VIIIA - Noble
Gases Other Groups ( Vertical and Horizontal
Groups) Group IB - 8B - Transition Metals Period
6 Group - Lanthanides (Rare Earth
Elements) Period 7 Group - Actinides
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The Periodic Table of the Elements
H
He
O
N
C
B
Li
Be
Ne
F
S
P
Si
Al
Na
Mg
Ar
Cl
Se
As
Ge
Ga
Zn
Cu
Ni
Co
Fe
Mn
Cr
V
Ti
Sc
K
Ca
Kr
Br
Te
Sb
Sn
In
Cd
Ag
Pd
Rh
Ru
Tc
Mo
Nb
Zr
Y
Rb
Sr
Xe
I
Po
Bi
Pb
Tl
Hg
Au
Pt
Ir
Os
Re
W
Ta
Hf
La
Cs
Ba
Rn
At
Ac
Fr
Ra
Rf
Sg
Du
Bo
Ha
Me
The Halogens
The Alkali Metals
The Alkaline Earth Metals
The Noble Gases
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Figure 2.14 A modern form of the periodic table.
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Chemical Compounds and Bonds
Chemical Bonds - The electrostatic forces that
hold the atoms of elements
together in the compound.
Covalent Compounds - Electrons are shared
between atoms of different elements to
form Covalent Cpds.
Ionic Compounds - Electrons are transferred from
one atom to
another to form Ionic Cpds.
Cations - Metal atoms lose electrons to form
ions.
Anions - Nonmetal atoms gain electrons to form
- ions.
Mono-atomic ions form binary ionic compounds
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Figure 2.16 Molecular and structural formulas
and molecular models.