Download Atomic History

Atomic History
Democritus
Dalton
JJ Thomson
Rutherford
Chadwick
Bohr
Matter is composed of empty
space in which atoms move
Elements consist of atoms and
compounds are collection of
atoms
“Plum pudding model” : Atoms
contain negative particles called
electrons
Alpha particles, positive charge
with a mass 7500x of electron.
Proved the pp model was wrong.
Nucleus center ( +) and tiny
electrons moved in space around
it.
Found neutrons(slightly more
massive than a proton.
Electrons are in circular paths
depending on their energy levels
Atomic History
De Broglie
Shrodinger
Millikan
Moseley
electrons move in waves rather
than straight circular paths
Wave Mechanical Model or
Quantum Mechanical Model.
Furthered De Broglie’s idea of
waves by stating that electrons
are in clouds but in certain energy
region
Oil drop experiment: discovered
that atoms had positive and
negative charges and that they
equal each other
Helped to arrange atoms in the
periodic table. Atoms were
arranged in increasing atomic
number using wavelengths and
xrays
Atoms, Isotopes and Ions
How do atoms of different
elements differ?
The Modern View of Atomic
Structure
What are the particles that make up an
atom and how do they differ from one
02m14an1
another?
proton
mass = 1 charge = +1
neutron
mass = 1 charge = 0
electron
mass = “0” charge = -1
02m14an1.mov.lnk
atoms have equal numbers of protons
and electrons so they are electrically
neutral
1/1840
Atomic Number
Atomic number
Number of protons in an atom
Identifies the element
6
C
Carbon
12.01115
Atomic Number
Use the Periodic Table to complete the
following.
1.
2.
What element has the atomic number 18?
What element has 35 protons?
How are atoms of one element
different from those of another
element?
They have different numbers of these
subatomic particles.
Atomic Number
Chemical Symbol
Element Name
Average Atomic Mass
1
H
Hydrogen
1.00797
Isotopes
Isotopes
How do we distinguish between atoms?
Do all atoms of an element have the same
composition?
Heavy Water and Water Ice Cube in
water
atom_parts.exe.lnk
Isotopes
Isotopes
What implication does this have for the masses
of atoms?
nuclear_particles.exe.lnk
Average atomic mass
Isotopes differ only in the number of Neutrons
Difference is shown by their mass numbers
Notation: superscript for mass number, which is
the sum of the number of protons and neutrons
Notation: subscript for atomic number, which is
the number of protons (and electrons)
Nuclear
Nuclear Particles
Particles
How many of each particle are in these
atoms?
76 Br
78 Br
80 Br
35
35
35
14 N
7
15 N
7
18 O
8
17 O
8
16 O
8
15 O
8
Ions
When an atom loses or gains electrons
and acquires a net electrical charge.
Gain electrons – negative ion - anion
Lose electrons – positive ion - cation
Mg
Mg2+
Ions
Charge of ion = # of protons - # of electrons
How many protons, neutrons and electrons
does 4120Ca2+ have?
How many protons, neutrons and electrons
does 7835Br - have?
Classwork
Atomic and Isotopic Symbols
10 min
How do we know what makes
up an atom?
What
What do
do atoms
atoms look
look like?
like?
See the electron microscope image of the
molecular art drawn with CO molecules.
See the image of graphite. Are these images
proof of atoms? How do we see atoms?
benzene
nickel
Surface
Surface Imaging
Imaging
What can we learn about atoms from video
generated by electron microscopy?
Ex. What do you know about silver?
Silver surface.MOV
Silicon surface.MOV
Cathode Ray Tubes
Why does the beam bend?
Gold
Gold Foil
Foil Experiment
Experiment
Examine the diagram of Rutherford’s alpha ray
experiment. What is the implication of this
experiment?
atomic Au foil.MOV
Gold Foil Exp.MOV
Line Spectra
700
650
600
550
500
450
400
350
Observation of unique line spectra
led to Quantum Theory
E=hν
Fourth
Third
Second
First
Nucleus
Where all of this has lead to
Bohr Model – did some good things but it
is not the whole truth.
Some
Some Questions
Questions
Color arises from electrons shifting from one
orbital to another of different energy
Na excitation.MOV
Ground state and excited state
What shift would give rise to emission of light?
to absorption of light?
absorb_emit.exe
How do fireworks emit light?
Demo
Sr, K, Li, Cu, Na
Where all of this has lead to
Quantum Model
What is the Quantum Mechanical
Model?
It predicts quantized energy levels for
electrons, like the Bohr model.
What is the Quantum Mechanical
Model?
It does not describe the exact path that
electrons take around the nucleus of an
atom, but is concerned with the
probability of an electron being in a
certain place.
Nucleus
Orbitals
Areas where an electron can be found
Can have up to two electrons
Fuzzy boundaries → “Electron Cloud”
The Closed Sphere Model
For convenience
Shows where the electron is 90% of the
time
The Heisenberg Uncertainty
Principle
You can never know exactly where an
electron is if you know how exactly fast it
is moving.
You can never know exactly how fast an
electron is moving if you know exactly
where it is.
The Atom is a Scientific Model
With the scanning tunneling microscope
we can see atoms, but we still cannot see
their internal structure.
Scientific models are created by
experiments, but are often modified.
There may be flaws in the current model.
THE END
Flame Test
What can you see? Why does it have
different colors?
Line Spectra
700
650
600
550
500
450
400
350
Observation of unique line spectra
led to Quantum Theory
E=hν
Fourth
Third
Second
First
Nucleus
Bohr's
Bohr's Model
Model
Model of
electrons
in fixed
orbits to
explain
quantization
Transitions
between
orbits
emits or
absorbs
light 07m07an1
07m07an1.mov.lnk
Figure 6.14
Today we use aspects of line
spectrum to identify elements,
compounds and mixtures?
UV-Vis Spectrometer
Distances and types of stars
Blood test- carbon monoxide poisoning
Mobile weapons detectors
Chlorophyll
How we determine these energy
levels
Orbital Diagrams and Electron
Configurations
n = Principle quantum number
Describes the energy level the electron occupies
n=4
n=3
n=2
n=1
Valence Shell
The number of electrons in the outer most
energy level.
Example: Lithium
Li has 1 electron in valence shell
Electron Dot Structure
Shows the number of valence electrons of
the element in a dot structure.
Octet rule: 8 electrons is the maximum
allowed electrons in a valence shell!
Mg
Li
O
Ne
Practice
Create a Bohr model, valence electrons?,
Electron Dot diagram of each:
Nitrogen
Calcium
Argon
Orbital Energy Levels
Shape of orbital
designated by the
letters
s, p, d, f, g
Excited states
Ground state
Shapes
Shapes of
of Orbitals
Orbitals
Shape of orbital designated by the letters
s, p, d, f, g
Orbitals have
different shapes
Describe
the motion
of an electron
in an orbital.
Combination
of electron
microscopy
and x-ray
diffraction
produced
image of
orbitals
Sets
Sets of
of Orbitals
Orbitals (Subshells)
(Subshells)
Depending on the type of orbital, we find that
they occur in sets differing in their
orientation in space
s - set of 1
p - set of 3
d - set of 5
f - set of 7
Orbitals.exe.lnk
Sizes of orbitals
Size depends on the value of n
Orbitals with the same n are about the
same size
Shape Orbital Diagram
Hydrogen
Chlorine
Electron
Electron Configurations
Configurations of
of
Some
Atoms
Some
Atoms
The
The
first
ten
elements
1s1
1s2
1s2 2s1
1s2 2s2
1s2 2s2 2p1
1s2 2s2 2p2
1s2 2s2 2p3
1s2 2s2 2p4
1s2 2s2 2p5
1s2 2s2 2p6
Shorthand
Shorthand Notation
Notation for
for Orbitals
Orbitals
Combinations of first two quantum
numbers; number of orbital types equals
the shell number (n).
1s
2s, 2p
3s, 3p, 3d
4s, 4p, 4d, 4f
5s, 5p, 5d, 5f, (5g)
6s, 6p, 6d, 6f, (6g, 6h)
Aufbau Principle
Aufbau Principle: start with the nucleus
and empty orbitals, then “build” up the
electron configuration using orbitals of
increasing energy
Aufbau.exe
Electron
Electron Configurations
Configurations
Electron Spin and Pauli Exclusion
Principle:
Only two electrons can occupy a
single orbital and they must have
opposite spins
Electron Configurations
Hund's Rule:
When filling a subshell, such as the
set of 3 p orbitals, place 1 electron
in each before pairing up electrons
in a single orbital
Electron Configurations
Arrangement of electrons in the orbitals is
called the electron configuration of the
atom
The ground state configuration can be
predicted, using the Aufbau Principle, the
Pauli Exclusion Principle, and Hund’s Rule.
Electron configurations
Filling _ rules.exe
How do we know what the filling
order is?
What chemistry tool might we rely on?
Electron
Electron Configurations
Configurations and
and
the
the Periodic
Periodic Table
Table
Valence electron configurations repeat
down a group
aufbau.exe.lnk
Ground state electron
configurations
Example: Li
atomic number = 3
nucleus has 3 protons
neutral atom has 3 electrons
2 electrons in 1s orbital, 1 electron in 2s orbital
2s
1s
Different ways to show electron
configuration
Energy level diagram
Box notation
↑↓
1s
2s
↑
2s
1s
Spectroscopic notation
Li 1s2 2s1
Read this “one s two”
not “one s squared”
Write the superscript 1.
Don’t leave it blank
Practice
Electron configuration wksht
Using the Periodic Table
The last subshell in the electron configuration is one of
these
(row #) s
(row # – 1) d
(row #) p
(row # – 2) f
Electron configuration of O
Atomic number of O = 8 so neutral atom has 8 e–
Electron configuration of Co
Atomic number of Co = 27 so neutral atom has 27 e–
Simplifying electron
configurations
Build on the atom’s noble gas core
↑↓ ↑↓ ↑↓ ↑
Ar
Co
Co
↑↓ ↑↓
1s
1s
He 1s2
O 1s22s22p4
O [He]2s22p4
2s
2s
2p
1s22s22p63s23p6
1s22s22p63s23p64s23d7
[Ar]4s23d7
↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑
2p
3s
3p
4s
↑
3d
↑
↑
Noble Gases
Far right of the periodic table
These elements are extremely unreactive
or inert
They rarely form compounds with other
elements
Noble Gas electron configurations
What is the electron configurations for
Neon
Abbreviated way to write configurations
Start with full outer shell then add on
Br
Ba
Noble Gases
Neon- emits brilliant light when stimulated by
electricity – neon signs- 4th most abundant
element in the universe.
Helium- light non reactive gas- used balloonsinexpensive, plentiful and harmless
Radon- radioactive gas- can cause cancercolorless, odorless emitted from for certain rocks
underground
Electron configuration of Sn
Locate Sn on the periodic table
Electron configuration of Sn
Sn [Kr]
The noble gas core is Kr
Electron configuration of Sn
Sn [Kr]5s2
The noble gas core is Kr
From Kr, go 2 spaces across the s-block in the 5th row
→ 5s2
Electron configuration of Sn
Sn [Kr]5s24d10
The noble gas core is Kr
From Kr, go 2 spaces across the s-block in the 5th row → 5s2
Then go 10 spaces across the d-block on the 5th row → 4d10
note: n = row – 1 = 5 – 1 = 4
Electron configuration of Sn—
done
Sn [Kr]5s24d105p2
The noble gas core is Kr
From Kr, go 2 spaces across the s-block in the 5th row → 5s2
Then go 10 spaces across the d-block on the 5th row → 4d10
note: n = row – 1 = 5 – 1 = 4
Finally go 2 spaces into the p-block on the 5th row → 5p2
Why are we doing all of this?
Properties of atoms correlate with the
number and energy of electrons
Electron configurations are used to
summarize the distribution of electrons
among the various orbitals
Practice
Practice
3-3 Practice
Write the complete electron
configurations and noble gas
shorthand #1-4
Practice
Refer to a periodic table and write the
electron configurations of these atoms.
Write the configurations using shorthand
notation.
Zn
I
Cs
1.
2.
The f-block is inserted into to
the d-block
Find the electron configuration
of Au
Locate Au on the periodic table
Find the electron configuration
of Au
Au [Xe]
The noble gas core is Xe
Find the electron configuration
of Au
Au [Xe]6s2
The noble gas core is Xe
From Xe, go 2 spaces across the s-block in the 6th row
→ 6s2
Find the electron configuration
of Au
Au [Xe]6s24f14
The noble gas core is Xe
From Xe, go 2 spaces across the s-block in the 6th row
→ 6s2
Then detour to go 14 spaces across the f-block → 4f14
note: for the f-block, n = row – 2 = 6 – 2 = 4
Find the electron configuration
of Au
Au [Xe]6s24f145d9
The noble gas core is Xe
From Xe, go 2 spaces across the s-block in the 6th row → 6s2
Then detour to go 14 spaces across the f-block → 4f14
note: for the f-block, n = row – 2 = 6 – 2 = 4
Finally go 9 spaces into the d-block on the 6th row → 5d9
note: for the d-block, n = row – 1 = 6 – 1 = 5
Electron configuration of ions
What is an ion?
How many electrons does Cl1- have?
How many electrons does Ca2+ have?
What is the electron configuration for the
chloride ion?
What is the electron configuration for the
calcium ion?
What do you notice?
Practice
Draw the orbital diagram for sulfur.
What ion does sulfur want to form and why?
Draw the orbital diagram for Potassium.
What ion does sulfur want to form and why?
What does this mean
Properties of atoms correlate with the
number and energy of electrons
Atoms like to have full outer shells.
Why is this important
Valence electrons
Electrons in the outermost energy level
Where all the action occurs
Practice
Whiteboard - Atomic Structure (continued)
Team
Write the electron configuration for silver.
Write the noble gas configuration for silver.
What element has the following electron
configuration?
1s22s22p6 3s23p64s23d4