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8/11/2019 Atomic Theories and Structures
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Thales
Matter:
water earth air
Leucippus(450 B.C.)
There must ultimately be tinyparticles of water that could not
be subdivided
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Democritus 470370 B.C.
- expanded Leucippus idea
- world made up of empty space and tiny
particles
atomos indivisible
- All forms of matter were divisible into invisible
particles called atoms
Empedocles (440 B.C.)
All matter was composed of four
elements:
Earth, air, water and fire
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Heat, cold, moisture and dryness
ex: fire = hot and dry
water = cold and moistair = hot and moist
earth = cold and dry
Endorsed and advanced the Empedocleantheory.
Believed that matter was continuous and
was not made up of smaller particles
hyle
Aristotle (384 - 322 B.C.)
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He offered logical hypothesis about the
existence of atoms by studying certain
experimental observations made by
other scientists concerning chemicalreactions
JOHN DALTON
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Antoine Laurent Lavoisier
When a chemical change occurred
in a closed system, the mass of theproducts after a chemical change
equals the mass of the reactants
before the change. In all tests, the
mass remained constant.
LAW OF CONSERVATION OF MASS OR MATTER
In ordinary chemical reactions, matter is neither
created nor destroyed.
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Joseph Proust
Specific substances always contain elementsin the same ratio by mass
LAW OF DEFINITE PROPORTIONS
LAW OF MULTIPLE PROPORTIONS
AmadeoAvogadro (1811)
Joseph Louis Gay-Lussac (1778-1823)
AVOGADROS LAW OF MOLAR VOLUMES
The ratio of masses of one element that combine
with a constant mass of another element can be
expressed in the ratio of small whole numbers
LAW OF COMBINING VOLUMES
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DALTONS ATOMIC THEORY
1. All matter is composed of
extremely small particles called
atoms.
2. Atoms of a given element are alike
in size, mass and other properties;
atoms of different elements differ
in size, mass and other properties.
3. Atoms cannot be subdivided,
created, or destroyed.
4. Chemical compounds are formed
when atoms of different elements
combine in simple, whole numberratios.
5. In chemical reactions, atoms are
combined, separated or
rearranged.
MODERN MODIFICATIONS OF
DALTONS ATOMIC THEORY
1. Discovery of the sub-atomic
particles of atoms.
2. Discovery of radio-isotopes.
3. Nuclear reactions.
4. Unmodified.5. Unmodified for simple
chemical reactions.
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An atomis the smallest particle of an element that can
exist either alone or in combination with other atoms.
Plum Pudding ModelRaisin Bread Model
Sir J.J. Thompson
Composed of a positively chargedcloud with the electrons distributed /
suspended
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Ernest RutherfordBritish
physicist
Miniature Solar System with
electrons moving around like
planets around the nucleus
Neils BohrDanish physicist
Postulated further that electronscould only move in certain orbits
and has certain energies
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Erwin SchrodingerAustrian physicist
Electrons are described not by the paths
they take but by the regions of space where
they are most likely to be found
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Negative electrical charge (-1)
Mass 9.110 x 10-24g ; Mass in amu =5.486 x 10 -4amu
Discovered by Sir Joseph John Thompson
in 1897
Positive electrical charge (+1)
Mass 1.673 x 10-24g ; Mass in amu = 1.0073
amuDiscovered by Eugene Goldstein (German
physicist) in 1886
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Bears no electrical charge; neutral no
Mass 1.675 x 10
-24
g ; Mass in amu =1.0087 amu
Existence was first predicted by
Rutherford; First evidence of the particle
was obtained by Walter Bothe in 1930and was finally discovered by James
Chadwick
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Is a theory that describes mathematically the wave
properties of electrons and other very small particles
Erwin SchrodingerSchrodinger Wave Equation
-Incorporates both the wavelike and particle-like behavior
of the electrons moving around a nucleus
- opened a way of dealing with the sub-atomic particles -QUANTUM MECHANICS the foundation for modern
quantum theory
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1) sorbital sharp - high probability
of being found rightat the nucleus
itself
- spherical cloud
2) porbital principal - cloud with 2 lobes
on opposite sides
of the nucleus
- has 3 p-orbitals
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Erwin Schrodinger found each atomic orbital can be
identified by four different numbers
-Are numbers used to identify electrons in the different
atomic orbitals
-specify the properties of atomic orbitals and theirelectrons
1. Principal Quantum Number ( n )- indicates the main energy levels surrounding a
nucleus; identifies the shell or energy level to which
the electron belongs
- values of n: 1,2,3 .
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2. Orbital Momentum Quantum Number ( l)
- indicates the shape of an orbital; also the quantum
number that indicates the type of sub-shell (sub-
levels)- s, p, d, and f
- widely known or called as the Azimuthal Quantum
Number
3. Magnetic Orbital Quantum Number (ml)
- quantum number that specifies the individual
orbital of a particular shape / sublevel
- s orbitalsphere centered on the nucleus- p orbital3 orientations
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4. Spin Magnetic Quantum Number ( ms)- indicates the 2 possible states of the spin of an
electron in an orbital
- refers to the relative spin direction of the electron+1/2 and -1/2
Is the arrangement of electrons in atoms
Also known as the Electron Distribution Mnemonics
GROUND STATE
EXCITED STATE
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1. Aufbau Principle
An electron occupies the lowest energy orbital that
can receive it
2. HundsRule
When electrons occupy orbitals of equal energy
levels, an electron occupies each orbital before
there is any pairing
3. Paulis Exclusion Principle
No more than two electrons may occupy any given
orbital
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1S 2S 3S 4S 5S 6S 7S
2p 3p 4p 5p 6p 7p
3d 4d 5d 6d 7d
4f 5f 6f 7f
S < 2
p < 6d < 10
f < 14
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Construct the electronic configuration of the following
elements, determine the number of energy levels with the
# of electrons per energy level and indicate the number of
valence electrons:
1. Cobalt = 27 6. Lead = 82
2. Gallium = 31 7. Tungsten = 74
3. Krypton = 36 8. Zirconium = 40
4. Bromine = 35
5. Antimony = 51
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