Download Atomic Theory & the Periodic Table

Atomic Theory & the
Periodic Table
A Review
Atomic History
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Ancient Greeks
Alchemists
John Dalton
Dmitri Mendeleev
JJ Thomson
Sir William Crookes
Ernest Rutherford
HGJ Moseley
James Chadwick
Neils Bohr
Erwin Schrödinger
Ancient Greeks (~ 400 B.C.E)
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Democritus (460 – 370 B.C.E.)
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All matter is made of tiny,
indestructible units called
ATOMOS
Aristotle (384 – 322 B.C.E) &
Plato (428 – 348 B.C.E)
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Completely disagreed with
Democritus. Public opinion
sided with these guys that all
matter was made of EARTH,
AIR, FIRE, & WATER
Alchemists (next 2000 years)
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People who tried to
get rich by turning
base metals (like iron
or lead) into gold.
 Some
were con artists
 Some were scientists.
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Discovered elements
like mercury, sulfur, and
antimony
John Dalton (1766 – 1844) &
Dalton’s Atomic Theory
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John Dalton
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Chemist & Physicist who
made a living teaching
 His theory is backed by many
experiments
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Theory
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Elements are made of
particles called atoms
All atoms of an element are
identical
Atoms of 1 element are diff.
from atoms of another element
Atoms of elements can
combine to form compounds
with simple, whole number
ratios
Atoms can’t be destroyed or
created, they’re just
rearranged in a chemical
reaction
Dmitri Mendeleev: 1834-1907
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Dmitri realized that
the properties of
some elements
repeat in a regular
pattern so he
organized them into
the 1st recognized
periodic table.
Sir William Crookes: 1832 1919
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Studied cathode ray
tubes and realized
that the rays travelled
in straight lines.
Believed they
represented a 4th
state of matter:
radiant matter.
JJ Thomson (1856 – 1940) & the
Cathode Ray Experiment (1890s)
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Physicist who used a
cathode ray tube to
show that atoms of
any element can be
made to give off tiny
negative particles
(ELECTRONS)
JJ’s Model- The Plum Pudding Model
(Chocolate Chip Cookie anyone?)
Ernest Rutherford (1871 – 1937) &
Gold Foil Experiment (1911)
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Ernest
the positive α (alpha) particles to
pass straight through to the back of the
detector. He was surprised when they
bounced off at strange angles.
 He surmised that the alpha particles were
bouncing off a small + charge in the Gold
atoms. He called that part the NUCLEUS!
 Expected
HGJ Moseley: 1887 - 1915
Realized that atomic numbers are not just
arbitrary numbers but represent the
number of protons in the nucleus of the
atom and that the periodic table is better
arranged according to atomic number
rather than atomic mass.
 Father of the modern periodic table
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Gold Foil Experiment
Some More Stuff Ernie Did
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In 1918 – He experimented by
bombarding N2(g) with alpha
particles. 1 of the results was
that a whole lot of H2(g) was
created. What’s going on?
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Ernie figured out that the H
atoms must have come from
inside the N2. That means that
ATOMS ARE DIVISIBLE!!!!!!!!
He eventually isolated those H
atoms and discovered they
were actually PROTONS
Ernie found a friend- James
Chadwick (1932).
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Ernie’s assistant, James Chadwick found the
NEUTRON in 1932.
 He
put some Be in a chamber with Po (gives off alpha
particles). The alpha particles hit the Be which gave
off some particles at high, high speeds. At first he
thought they were gamma (γ) rays but they moved too
fast for gamma rays. He worked his way thru some
calculations and discovered they were not, but some
neutral particles that he named (NEUTRONS)
Chadwick- Rutherford Model
Neils Bohr (1885 – 1962) and the
Bohr Planetary Model
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Developed a theory of
the H atom, saying
that electrons moved
in specific ORBITS
around the nucleus.
Each orbit has a
specific amount of
energy to it.
Erwin Schrödinger: Modern Model of
the Atom (Wave Mechanical Model)
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States that electrons
exist in a state
described by an
ORBITAL
 An
area where there is
a 90% probability of
finding an electron
ATOMIC STRUCTURE
Physical structure
 Atomic Number
 Mass Number
 Isotopes
 Atomic Mass
 Calculating Atomic Mass
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Atomic Structure
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An atom is the defining
part of what makes an
element, an element.
Cannot be broken down
chemically.
Atoms are mostly empty
space!
Atoms are very, very
small!
Atomic Structure
Particle
Relative Mass
(Actual Mass)
Relative Charge
Proton
1836
+1
(1.67262158 × 10-27
kg)
Neutron
1839
0
(1.67492729 × 10-27
kg)
Electron
1
(9.10938188 × 10-31
kg)
-1
Atomic Number & Mass Number
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Atomic Number = # of
protons (p+)
=
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# electrons (e-)
Mass Number
= # of p+ + # n0
How many p+, n0, and e-?
238
92
U
23
11
Na
Isotopes
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Atoms of an element that have different
#’s of neutrons.
 1 1H
2
1H
 63Li
7
3Li
3
1H
Atomic Mass
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Weighted average of all the masses of
each isotope of the element.
A.M. =
(% isotope 1)(Mass isotope 1) + (% isotope 2)(Mass isotope 2) + …
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Examples
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Calculate the average atomic mass of gold
of 197Au weighs 197
 50% of 198Au weighs 198
 50%
Electron Configurations
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Way of describing which orbitals electrons
are within the atom.
7
principal orbitals [n] (energy levels)
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4 sublevels (s, p, d, f)
e- - electrons in the highest orbital
(energy level)
 Valence
Orbital Sub Levels
s
d
p
f
Orbital Filling Diagram
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s sublevels can hold 2
ep sublevels can hold
6 ed sublevels can hold
10 eF sublevels can hold
14 e-
Electrons and Light
Valence electrons
 Electromagnetic Spectrum
 Light characteristics
 Electrons and Light
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Valence e
Fe – 1s22s22p63s23p64s23d6
{2 valence e-}
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Rb – [Kr]5s1
{1 valence e-}
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Cl – [Ne]3s23p5
{7 valence e-}
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These are the electrons that are involved in
bonding and chemical reactions!!!!!!!
Valence Electrons and the
Periodic Table
What do e- have to do with light?
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When you add energy to an element (perhaps
by heating it up), the valence e- get “excited”. In
other words they jump up to a higher energy
level or orbital.
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BUT… they are unstable up there. So they
release that added energy in the form of colored
light!
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Huh?
Electromagnetic Spectrum
Light Characteristics
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Light moves in wave
from the light source
to you eye or other
detector!
Waves have several
characteristics!
Wave Characteristics
c = λ× ν
c = speed of light
= 3.00 × 108 m/s
λ = wavelength
ν = frequency
Light can also act as particles, we
call them PHOTONS!!!!!!
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Moving along those waves, there are little
packets of energy called photons.
 Photons
have specific amounts of energy as
determined by the frequency of the light.
E
=h×ν
 The
higher the frequency of the light, the more energy
the light has.
So how does light tie into excited
electrons?
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When you add energy to an element, it’s
valence e- absorb that packet of energy &
become unstable. In order to return to
stability (lower their energy) they “spit out”
that energy in the form of a photon that
has a frequency in the visible light part of
the electromagnetic spectrum that we can
see.