Download Unit 7 Notes - Mahtomedi High School

Unit 7 Notes
UNIT 7: Modern Atomic Theory
Review
1/24/2012
Atomic Theory • JJ Thomson's so far
Plum Pudding Model
• Everyone at that time imagined the
atom as a "Plum Pudding." (Thomson‛s
Model) Scientist believed the atom
had the same consistency
throughout, with negatively-charged
electrons scattered about in it like
raisins in a pudding.
Gold Foil Experiment (Rutherford)
• Earnest Rutherford's View of the Atom
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Rutherford's Model
Rutherford's Atom
• As part of an experiment with x-rays in 1909, Rutherford was
shooting a beam of alpha particles at a sheet of gold foil, and
tracing the particles' paths.
• Alpha particles are a type of ionizing radiation ejected by the
nuclei of some unstable atoms. They are large subatomic
fragments consisting of 2 protons and 2 neutrons.
• Most of the particles went through the foil, which would be
expected if the atoms in the gold were like a plum pudding. But
every now and then, a particle bounced back as though it had hit
something solid.
Aug 31­8:56 AM
Chemistry
1/24/2012
Unit 7 Notes
1/24/2012
UNIT 7: Modern Atomic Theory
Rutherford's Model
Rutherford's Atom
(continued)
• After tracing many particles and examining the patterns,
Rutherford deduced that the atom must have nearly all its mass,
and positive charge, in a central nucleus about 10,000 times
smaller than the atom itself.
• All of the negative charge was held in the electrons, which
must orbit the dense nucleus like planets around the sun.
• The major problem with Rutherford‛s model was that it
couldn‛t explain why the negative electrons weren‛t attracted
into the positive nucleus, causing the atom to collapse.
Aug 31­8:56 AM
1/25/2012
UNIT 7: Modern Atomic Theory
Energy and Light
(continued)
• Properties of Waves
Wavelength, Frequency, Crest and Trough
Wavelength
Amplitude
Energy and Light
Crest
Trough
• Wavelength (λ): the distance between two adjacent crest or two adjacent troughs.
• Frequency (f ): the number of waves (cycles) per second that pass a given point in space
• Relationship: Wavelength and frequency are inversely related
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Energy and Light
Energy and Light
1/25/2012
• Electromagnetic Radiation: radiation consisting of self­sustaining oscillating electric and magnetic fields at right angles to each other and to the direction of propagation. It does not require a supporting medium and travels through empty space at the speed of light. • Gamma Rays­wavelength: 0.01 nm • X­rays ­1 nm • Ultra­violet Rays­0.1 micrometres • Visible Light­ Red light: 0.7 micrometres • ­ Violet Light: 0.4 micrometres • Infrared Radiation­ 0.01 mm • Microwaves­less than 10 cm, usually 1cm • Radiowaves­ Long, Medium and Short Waves:2km­10m • ­Very High Frequency (VHF) and Ultra High Frequency (UHF): 10m­10cm Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Energy and Light
Energy and Light
(continued)
1/25/2012
• Photon: packets of energy (energy is directly related to frequency)
• Visible light exhibits both wave and particle like properties.
• Light has properties of both waves and particles "Wave­Particle Duality"
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Light and Energy
Energy Emissions
Energy
Excited Li atom
1/26/2012
• Ground State - the lowest possible energy state
of an atom or molecule.
• Excited State - atoms with extra energy.
Electrons are farther away from the nucleus than
they usually are.
Photon of Red Light
Emitted
Li atom in
lower energy state
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Light and Energy
Energy Emissions
1/26/2012
• When atoms receive energy from some source they become excited
• They can release this energy by emitting light.
• The energy is carried away by a photon.
• The energy of the photon corresponds exactly
to the energy change experienced by the atom.
• This determines what color of light is released
by the atom.
(Color of photon emitted
depends on energy change)
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Hydrogen and Bohr
Energy Emissions
1/26/2012
• Suppose we take a sample of hydrogen atoms and put a lot of
energy into the system.
• When we study the photons of visible light emitted, we see
only certain colors. That is, only certain types of photons are
produced. This is a very significant result. Because only
certain photons are emitted, we know that only certain energy
changes are occurring.
• This means that the hydrogen atom must have certain
discrete energy levels. Excited hydrogen atoms always emit
photons with the same discrete colors (wavelengths). We can
conclude that all hydrogen atoms have the same set of discrete
energy levels.
• We say the energy levels of hydrogen are quantized. This
means that only certain values are allowed. Scientists have
found that the energy levels of all atoms are quantized.
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Hydrogen and Bohr
Energy Emissions
Aug 31­8:56 AM
Chemistry
1/26/2012
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Hydrogen and Bohr
1/27/2012
Bohr
• Continuous versus discrete • Continuous allows for you to be anywhere along the range [(a) like a ramp]
• Discrete you can only be at certain points along the range [(b) like a staircase]
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Hydrogen and Bohr
Bohr
• In 1912 Bohr joined Rutherford. He realized that Rutherford's model wasn't quite right. The orbiting electrons should give off energy and eventually spiral down into the nucleus, making the atom collapse. Or the electrons could be knocked out of position if a charged particle passed by. • Bohr suggested the revolutionary idea that electrons "jump" between energy levels (orbits). Thus when an atom absorbs or gives off energy (as in light or heat), the electron jumps to higher or lower orbits. Bohr published these ideas in 1913 to mixed reaction. But there was good evidence he was right: the electrons in his model lined up with the regular patterns (spectral series) of light emitted by real hydrogen atoms. • Unfortunately Bohr’s Model of the atom only worked for hydrogen and electrons do not move around the nucleus in circular orbits like planets orbiting the sun.
Aug 31­8:56 AM
Chemistry
1/27/2012
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Hydrogen and Bohr
1/30/2012
1/31/2012
Flame Test
Fireworks Video
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
1/30/2012
Wave­Mechanical • Victor de Broglie and Erwin Shrodinger
• Two Physicists
Model
• Due to the fact light exhibits both wave and particle nature...maybe the electron does too!
• Wave Mechanical Model
• Describes the electron states in terms of orbitals (NOT the same as orbits)
• Uncertainty principle: you can not pin­point the exact location at a particular time because the electrons are constantly moving. • (You can predict a region of probability that you would expect to find the electron ORBITAL)
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
1/30/2012
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
• Wave Mechanical Model
Wave­Mechanical • Firefly Experiment
• The picture is brightest where the Model
film has been exposed to the most light. The intensity of the color reflects how often the firefly visited a given point. • The probability map, or orbital that describes hydrogen in its lowest possible energy state
• Hydrogen Orbitals
• The probability of an electron decreases as...it gets farther from the nucleus
• 1s orbital (Sphere)
• The electron can be found inside the sphere 90% of the time
Aug 31­8:56 AM
1/30/2012
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
Wave­Mechanical • Principal Energy Level: Discrete energy levels where Model
electrons can be found
• Sublevel: s, p, d and f
• Principal energy levels can be divided into sublevels:
p
s
p
s
s
Aug 31­8:56 AM
Chemistry
d
p
s
(The first four Principal
Energy Levels of Hydrogen)
f
d
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
1/30/2012
• Orbitals: An orbital can contain two electrons with Wave­Mechanical paired spins and is often associated with a specific Model
region of an atom. • The 3 p orbitals
• Example: the 2nd Principal Energy level can be divided into 2s and 2p sublevels and individual orbitals
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
1/30/2012
Wave­Mechanical • Diagram of principal energy levels 1 and 2
Model
• The shape and labels of the five 3 d orbitals
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
1/30/2012
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
Wave­Mechanical • Diagram of the orbitals of s, p, d and f: Model
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Wave‐Mechanical Model
Wave­Mechanical • Summary of the orbitals:
Model
Principal Energy Level Sublevel Type
it first appears
Aug 31­8:56 AM
Chemistry
1/30/2012
Number of Number of electrons
Orbitals
Unit 7 Notes
Uncertainly Video
Jan 17­10:26 AM
UNIT 7: Modern Atomic Theory
Electron Configuration
2/1/2012
Electron • 3 Rules for writing Electron Configurations or Configuration Orbital Diagrams
• Aufbau Principle: Electrons enter lowest energy level first before moving to higher levels (build­up)
• Pauli Exclusion Principle: If electrons must pair together they will have opposite spins
• Hund's Rule: Within a sublevel, one e­ per orbital before pairing them. The maximum amount of electrons that can occupy a single orbital is 2.
___ ___ ___ • Ex: ____ ____ 1s 2s 2p
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
2/1/2012
UNIT 7: Modern Atomic Theory
Electron Configuration
• Orbital Diagram: using a diagram to represent the Electron Configuration electron arrangement and spin in atoms or ions
• Example: Nitrogen's orbital diagram: 2s
1s
2p
H
1s
2s
2p
1s
2s
2p
1s
2s
2p
1s
2s
2p
1s
2s
2p
1s
2s
2p
He
Be
C
O
Ne
Aug 31­8:56 AM
2/1/2012
UNIT 7: Modern Atomic Theory
Electron Configuration
• Electron Configuration: way to represent the Electron Configuration arrangement of electrons in atoms or ions
• Example:
A
B
A ­ Energy Level
2
1s
C
Chemistry
B
B­ # of electrons
C­ Sub­level
Nitrogen has 7 electrons, so the electron configuration for Nitrogen: 1s22s22p3
Aug 31­8:56 AM
A
4p5
C
s: 2
p: 6
d: 10
f: 14
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Electron Configuration
Electron Configuration
s: 2
p: 6
d: 10
f: 14
2/1/2012
H
He
Be
C
O
Ne
Fe
Rn
U
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Electron Configuration
Electron Configuration
Aug 31­8:56 AM
Chemistry
2/2/2012
Unit 7 Notes
2/2/2012
UNIT 7: Modern Atomic Theory
Electron Configuration
Electron Configuration
Valance Electrons
Aug 31­8:56 AM
2/2/2012
UNIT 7: Modern Atomic Theory
Electron Configuration
Electron Configuration 1
s
p
2
3
4
5
6
7
d (n­1)
f (n­2) 67
1s
1st Period
1
1st
of colum
s-b
n
loc
k
s-block
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
2/2/2012
UNIT 7: Modern Atomic Theory
Electron Configuration
Electron • Shorthand Configuration
Configuration
• Core e­: Go up one row and over to the Noble Gas.
• Valence e­: On the next row, fill in the # of e­ in each sublevel.
• Example ­ Germanium
[Ar] 4s2 3d10 4p2
Aug 31­8:56 AM
2/2/2012
UNIT 7: Modern Atomic Theory
Electron Configuration
s
Electron Configuration
1
2
3
4
5
6
7
s: 2
p: 6
Fe
d: 10
f: 14
p
d (n­1)
f (n­2) 67
Rn
U
Pb
Ra
W
Aug 31­8:56 AM
Chemistry
Unit 7 Notes
2/3/2012
UNIT 7: Modern Atomic Theory
Period Trends
Periodic Trends • Properties:
• Metals: Shiny, Malleable, Ductile and good conductors
• Non­Metals: Dull, Brittle and non­conductors
• Metalloids: Semiconductors, can be shiny and kinda malleable and ductile
• Activity Trends:
• Metals: More reactive the further down and to the left
• Non­Metals: More reactive the further up and to the right
• Atomic Size Trends:
• Atom get larger going down the family
• Atom get small going across the period
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Period Trends
Periodic Trends
Aug 31­8:56 AM
Chemistry
2/3/2012
Unit 7 Notes
UNIT 7: Modern Atomic Theory
Period Trends
2/3/2012
Periodic Trends
Why do atoms get bigger as you go down a family
on the periodic table?
Why do atoms get smaller as you go across a
period on the periodic table?
Aug 31­8:56 AM
UNIT 7: Modern Atomic Theory
Period Trends
2/6/2012
Periodic Trends
Periodic Trends Lab
Aug 31­8:56 AM
Chemistry
Attachments
Excited/Ground State h­atom
EM spectrum
electron config