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ATOMIC STRUCTURE
ATOM - smallest part of an element that can exist by itself.Cannot be created nor destroyed
The ATOM
400 B.C.- Democritus- invisible atom • Earth• Water• Air• Fire
The ATOMMiddle Ages- The ALCHEMISTS
Tried to change materials into Gold.
Failed, but developed lab techniques and discovered elements.
Atomic Theory
1803 John Dalton's Atomic Theory
Dalton's Atomic Theory
1. All matter composed of atoms.2. Atoms of elements are identical.3. Atoms cannot be created nor destroyed.4. Atoms are combined in specific ratio's.
Cathode Ray Tubes-
Electric currents pass through them.
Cathode Ray Tubes-1897 Sir Thomson-
Suggested that cathode ray tubes consists of (-) particles.These particles are deflected by both magnetic and electric fields.
Plum Pudding ModelDevised by Thomson.Negative “plums” surrounded by positive “pudding”.
ELECTRONS-
sub atomic particle.negatively charged1/1837th the mass of the proton.
ELECTRONS
Robert Millikan-1909 Oil drop experiment.Found the mass of an electron.
ELECTRONS-
Atoms are neutral, so there must be something positive (+).Electrons are small, so there must be something larger that accounts for the mass.
Lord Ernest Rutherford-
1908 Known for two major
experiments.
GOLD FOIL EXPERIMENT
Rutherford’s ExperimentBombarded metal foil with fast moving positive particles.
1 out of 8,000 bounced straight back.
Some powerful force repelled them.
Rutherford ModelThe atom is mostly empty space.The center must have a positive charge.This center must occupy a small amount of space.It is very dense.
NUCLEUS
Positive charged. Dense in center. Contains most mass little volume. Atoms mostly empty space,
electrons surround.
NUCLEUS
Contains nucleons which include neutrons and protons
PROTONS
Positive charged.Located in the nucleus.
NEUTRONS
Electrically neutral- no charge.Equal in mass to protons.Discovered by James Chadwick in 1932.
MASS DISCOVERED -28
Electron - 9.1 X 10 1/1837 Thomson 1897 -24
Proton + 1.67 X 10 1 Early 1900’s -24
Neutron 1.68 X 10 1 Chadwick 1932
Atomic Number
Number of protons. Protons determine the atom.Each element has its own unique number of protons Atomic number stays constant
Atomic Number
Mass Number (atomic mass)-
Total # of protons + neutrons
U-235 92 = Atomic NumberMass Number = 235 - 92 = neutrons ---------------------------------------
23 11 Na= 11 protons 12 neutron 11 electrons
Isotopes
Same element with different # of neutrons.Number of protons do not change.Nuclides - name given to any isotope
IONS
Charged atoms.Positive have lost electrons Negative have gained.
Atomic Mass Unit-AMU
Atomic Mass Unit (u) = 1/12 the mass of C-12 1.66 X 10 -24 g
Average Atomic Mass
Average Atomic Mass
Average Atomic Mass- weighted average of all Natural atomic masses.All isotopes put together by %
Cl=34.969u 47.3% Cl=36.966 u 52.7%
Average Atomic Mass
Average Atomic Mass = % (mass) + % (mass)
Average Atomic Mass
Find the Average Atomic Mass of element X. 40.7% weighs 13.78 grams, 30.3% weighs 14.12 grams, and 29.0% weighs 14.99 grams…
= .407 (13.78) + .303 (14.12) + .290
(14.99)
Electromagnetic Spectrum
Travel at speed of light 186,000 m/s
Can travel through a vacuum
Electromagnetic Spectrum
Radiowaves ------longest wavelength Microwaves infra- red ROY-G-BIV Ultra -violet X-ray Gamma------shortest wavelegth
The longer the wavelength– the slower the frequency
Quantum Theory
1900 Max Planck- German Physicist- light has particle like propertiesa Quanta is a finite quantity of energy.
Photoelectric Effect
Photoelectric Effect- The emission of electrons by
metals when light shines on it. Energy given off.
Quantum Theory
1905 Al Einstein-
Spectroscopy Spectroscopy- Study of the emission spectra of certain substances. Each atom gives off Specific lines. Continuous spectrum- separates into a band of colors that blend.Bright line spectrum - separate into specific lines of colors.
Spectroscopy
Each element has it's own specific bright-line spectrum. In this way, the composition of various substances may be found.
Bohr
Neils Bohr- (1913)
Bohr felt that electrons could only be in certain areas around the nucl eus.
Bohr Theory
Electrons revolve around nucleus in
specific energy levels.
Have specific orbits - K, L, M, N
Principle Energy Level, electron shells, + energy levels all mean the same.
Bohr Theory
Shell # of electrons (2n 2 )1 22 83 184 325 50
Bohr TheoryGround state- lowest energy state of atom.Excited state-higher energy state than ground. Electrons are further away.
Bohr Theory
Electrons normally in ground state.When heated they absorb energy and they jump to a higher excited state.
Bohr Theory
Instantaneously the electrons return to the ground state.They do this by releasing (emitting) photons.This can be seen by the various colors produced.
Bohr Theory
Normally in the ground state (closest).
Addition of energy makes the electrons jump to excited levels.
Energy emitted when they go from higher back to closer level.
Energy is released as photons (spectral lines)
Electron Configuration(regents level)
A way to designate electrons and the shells that they are in.Some examples include:
C 2-4 H 1 Na 2-8-1 Cl 2-8-7 K 2-8-8-1****all of these are in the ground
state
Electron Configuration
Some more examples:
O 1-7 Na 2-7-2 Al 2- 6- 5
*** these are all in the excited state
Electron Configuration IONS
+1 +3 -2 -1
K Al O Cl
Valence ElectronsValence Electrons are located in the outermost shell or Principle Energy Level.
OK TIME TO GET TOUGH!
Electron Cloud Theory-
1926 Erwin Schrodinger.
Electrons located in 3-D region called Orbitals.
Heisenberg Uncertainty Principle
Not possible to know exactly where the electron is.
We can only state the probability of finding a particle at a particular time and place.
Werner Heisenberg (1927)
Wave-Mechanical Model
DeBroglie
Wave-Mechanical Model
Electron Dot Diagrams
1916 G.N Lewis
Shows only valence electrons.
QUANTUM THEORY
Sub- Levels
These are the various shapes where electrons can be located.
s-p-d-f
s Orbitals
p Orbitals
d Orbitals
f Orbitals
QUANTUM NUMBERS
Principle quantum # 1, 2, 3 energy shells
Orbital quantum # s, p, d tells the shape
Magnetic quantum # shows the orientation P has three orbitals Px Py Pz
Spin quantum # (+) or (-) direction of electron’s spin
Quantum numbers describe the state of a particular electron.
Quantum Numbers- tells the properties of the orbitals and their electrons
Principle Orbital # of Orbitals Total e-
2 2
n 1 n 2n
1 s 1 2------------------------------------------------------------------------------------------------------------------------
2 s 1 2 p 3 6------------------------------------------------------------------------------------------------------------------------
3 s 1 2 p 3 6 d 5 10 ------------------------------------------------------------------------------------------------------------------------
4 s 1 2 p 3 6 d 5 10 f 7 14 tells energy shell tells the shape
(subshells)
Stupid People Die First
(n) 1 s
2 s p 3 s p d 4 s p d f orbital 1 3 5 7 electrons 2 6 10 14
Electrons will fill:
Ground State- Fills with the electrons as close to the nucleus as possible. Each electron will fill the area with the least amount of energy.The order of increasing energy:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s
Electron Configuration
Tells the arrangement of the electrons 2 2 6
1s 2s 2p
1,2 = shell
s,p,d = sub-levels
exponants = # of electronss has 1, p has 3, d has 5 orbitalsonly two electrons per orbital
THE APARTMENT!
*** Only two people per room1st floor: 1 Apartment 1 room, 2 people2nd floor: 2 Apartments- Apartment 2S has 1 room, 2 people Apartment 2P has 3 rooms, 6 people3rd floor: 3 Apartments Apartment 3S has 1 room, 2 people Apartment 3P has 3 rooms, 6 people Apartment 3d has 5 rooms, 10 people
2 2 6 2 6 2 10 6 2
1s 2s 2p 3s 3p 4s 3d 4p 5s
2 2 5
ground state 1s 2s 2p
2 1 6
excited state 1s 2s 2p 2 6 2
(or) 1s 2p 3s
STOP HERE
RULES
Orbital Notation
LITHIUM 1s 2s 2p
NITROGEN 1s 2s 2p 2p 2p
Aufbau Principle-Aufbau Principle-
Electron occupies the lowest energy orbital that can hold it.
Hund’s Rule-Hund’s Rule-
No orbital in a sublevel may contain 2 electrons until all contain one.
Pauli Exclusion Principle-
Pauli Exclusion Principle- No two electrons will have the same
four quantum #’s
TRY THESE NOW!!!!
Give the following configurations for each: 1) Regents level 2) Advanced level3) Orbital Notation Sulfur Magnesium Iron Phosphorus -2 Rubidium
Cu & Cr
Special cases
Cu---- Its 4s and 3d are very close.Its 4s moves to 3d to become completely filled.
2 9 1 10
4s 3d 4s 3d
4s 3d
Special cases
Cr ----- Its 4s and 3d are very close. One of the 4s moves to 3d, since half-
filled gives more stability.
2 4 1 5
4s 3d 4s 3d
4s 3d