arrangement of electrons in atoms (chapter 4) notes part 1 electromagnetic radiation
TRANSCRIPT
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Arrangement of Electrons in Atoms (Chapter 4) Notes
Part 1 Electromagnetic Radiation
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Let’s Review Energy!
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Let’s Review Energy!Radiation of different wavelengths affect matter differently – certain wavelengths (near infrared) may burn your skin with a heat burn, overexposure to X radiation causes tissue damage.
A. These effects are due to differences in the energy of the radiation.
B. Radiation of high frequency and short wavelength are more energetic than radiation of lower frequency and longer wavelength.
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I. Properties of Light-I. Different types of electromagnetic
radiation (x-rays, radio waves, microwaves, etc…) SEEM to be very different from one another.
II. All types of electromagnetic radiation (radiant energy) move through a vacuum at a speed of 3.00 x l08 meters per second.
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A. Wavelength – A. Distance between identical points on adjacent
wavesB. Symbolized by lambda, , C. Measured in any length unit, depending on the size
of the waveA. Ex. Shorter X-rays are usually measured in nanometers
or angstroms B. Ex. Longer radio waves might be measured in meters
or kilometers.
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Wavelength
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B. Frequency - A. the number of complete
wave cycles that pass a given point in one second:
B. Unit of frequency is cycles/second
C. Written as sec-1, or Hertz
D. The letter f or the letter “nu”,, is used to depict frequency.
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If the frequency and wavelength are known then the product of the two (wavelength x frequency) is always equal to the same speed. It is known as the speed of light or c.
c = speed of light = 3.00 x l08 m/s
c =f = wavelength (in m)
f = frequency (in Hz)
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1. What is the wavelength of radiation whose frequency is 6.24 x l013 sec-1?
A: 4.81X10-6 m
2. What is the frequency of radiation whose wavelength is 2.20 x l0-6 nm? (1 m = 1,000,000,000 nm)
A: 1.36X1023 s-1 or Hz
3. A television relay transmitter operates at a frequency of 927.9 MHz. Calculate the wavelength of the signal in nanometers. Is this visible light? (1 MHz = 1,000,000 Hz)
A: 3.233X108 nm – Not visible light.
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II. The Photoelectric Effect (pg 93) – refers to the emission of electrons from a metal when light shines on the metal.
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A. The wave theory of light (early 1900) could not explain the photoelectric effect.
A. Light was thought of as waves B. Light was known to be a form of energy, capable of
knocking loose an electron from a metal. C. But the wave theory of light predicted that light of any
frequency could supply enough energy to eject an electron.
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B. Scientists couldn’t explain why for a particular metal, no electrons were emitted if the light’s frequency was below a certain minimum.
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C. Explanation of the Photoelectric Effect by Max PlanckA. In 1900 Max Planck proposed that light consisted of
BUNDLES OF ENERGY called QUANTA. B. A quantum is the minimum quantity of energy that can be
lost or gained by an atom.
Max Planck
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Planck proposed the following relationship between a quantum of energy and the frequency of radiation:
E = hfh = Planck’s constant = 6.63 x l0-34 Joules sec E = energy (in Joules)f = frequency (in Hz)
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Examples:1. If a certain light has 7.18 x l0-19 J of energy what is the
frequency of this light? A: 1.08X1015 s-1or Hz
b. What is the wavelength, in nm, of this light? A: 278 nm
2. If the frequency of a certain light is 3.8 x l014 Hz, what is the energy of this light? A: 2.5X10-19 J
3. The energy of a certain light is 3.9 x l0-19 J. What is the wavelength, in nm, of this light? Is it visible?
A: 510 nm – Yes visible light.4. Calculate the smallest increment of energy that an object
can absorb from yellow light, the color given off when sodium atoms are heated in a flame. The wavelength of this light is 589 nm.
A: 3.37X10-19 J
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D. Albert Einstein Expanded on Planck’s Idea
A. Explained that while light exhibits many wavelike properties, it can also be thought of as a stream of particles each carrying a quantum of energy.
B. Einstein called these particles PHOTONS.
A. A photon is a particle of electromagnetic radiation having zero mass and carrying a (1) quantum of energy.
Albert Einstein
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C. Einstein explained the photoelectric effect by proposing that electromagnetic radiation is absorbed by matter only in whole numbers of photons.
D. The electron must be struck by a single photon possessing at least the minimum energy/frequency (Ephoton = hv) required to knock the electron loose
from a metal surface or the electron remains bound to the metal surface.
E. Electrons in different metals are bound more or less tightly, so different metals require different
minimum frequencies to exhibit the photoelectric effect.
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EXAMPLE
An atom or molecule emitting or absorbing radiation whose wavelength
is 589 nm cannot lose or gain energy by radiation except in MULTIPLES OF 3.37x l0-19 J. It cannot, for example, gain 5.00 x l0-19 J from this radiation
because this amount is not a multiple of 3.37 x l0-19.
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5. In astronomy, it is often necessary to be able to detect just a few photons because the light signals from distant stars are so weak. A photon detector receives a signal of total energy 4.05 x l0-18 J from radiation of 540 nm wavelength. How many photons have been detected?
A: 11 photons
6. Excited chromium atoms strongly emit radiation of 427 nm. What is the energy in kilojoules per photon?
A: 4.66X10-22 kJ
7. Light hitting certain chemical substances may cause rupture of a chemical bond. If a minimum energy of 332 kJ is required to break a carbon-chlorine bond in a plastic material, what is the longest wavelength of radiation that possesses the necessary energy?
A: 5.99X10-31 m
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III. The Hydrogen-Atom Line-Emission Spectrum
A. Investigators passed an electric current through a vacuum tube containing hydrogen gas at low pressure, they observed a characteristic pinkish glow.
B. When a beam of the emitted light was shined through a prism, it was separated into a series of specific frequencies (and therefore specific wavelengths, c =) of visible light. The bands of light were part of what is known as hydrogen’s LINE-EMISSION SPECTRUM. (page 95)
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III. The Hydrogen-Atom Line-Emission Spectrum
C. The lowest energy state of an atom is its ground state.
D. A state in which an atom has a higher amount of energy is an excited state. When an excited atom returns to its ground state, it gives off energy.
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IV. Bohr’s Model of Hydrogen – A. Incorporated Planck’s quantum theory to
explain line-emission spectra. B. Bohr said the absorptions and emissions
of light by hydrogen corresponded to energy changes within the atom. The fact that only certain frequencies are absorbed or emitted by an atom tells us that only certain energy changes are possible.
C. Bohr’s model incorporated (l) Rutherford’s Experiment, which established a nucleus and (2) Einstein’s theory that used Planck’s quantum theory to determine that light is discrete bundles of energy.
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Bohr’s Model of the Hydrogen Atom
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V. Bohr’s Theory of the Atom:A. Electrons cannot have just any energy; only orbits of
certain radii having CERTAIN energies are permitted.B. Thus, when an electron absorbs quanta of energy, it will
cause them to jump away from the nucleus to a higher orbit (energy level or n) and when the electron falls from a high orbit to a lower one, a photon of a particular wavelength is released, and a particular color will be given off.
C. The larger the value of n, the farther the electron is from the nucleus and the higher energy it possesses.
D. However, Bohr’s approach did not explain the spectra of atoms with more than one electron or the chemical behavior of atoms.
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V. Bohr’s Theory of the Atom:
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Electrons in Atoms (Chapter 4) Notes
Part 2 Quantum Model of the Atom
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So where are the electrons of an atom located?
A. Various Models of the Atom
Dalton’s Model
Thomson’s Plum Pudding Model
Rutherford’s Model
Bohr’s ‘Solar System’ Model – electrons rotate around the nucleus
Quantum Mechanics Model – modern description of the electron in atoms, derived from a mathematical equation (Schrodinger’s wave equation)
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B. In 1926, the Austrian physicist Erwin Schrodinger used the hypothesis that electrons have a dual wave/particle nature (developed by Louis de Broglie in 1924) to develop an equation that treated electrons in atoms as waves.
Erwin Schrodinger
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Electrons as WavesLouis de Broglie (1924)
Applied wave-particle theory to electrons
electrons exhibit wave properties
QUANTIZED WAVELENGTHS
Adapted from work by Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Standing Wave 200
150
100
50
0
- 50
-100
-150
-2000 50 100 150 200
Second Harmonic or First Overtone 200
150
100
50
0
- 50
-100
-150
-2000 50 100 150 200
Fundamental mode 200
150
100
50
0
- 50
-100
-150
-2000 50 100 150 200
Louis de Broglie~1924
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Electrons as WavesQUANTIZED WAVELENGTHS
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
n = 4
n = 6
Forbiddenn = 3.3
n = 5
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Schrodinger’s equation results in a series of so called wave functions, represented by the letter (psi).
Although has no actual physical meaning, the value of 2 describes the probability distribution of an electron. (Same concept covered in Algebra II when dealing with
linear regressions and finding best fit lines.)
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Electron Probability vs. Distance
Ele
ctro
n P
roba
bilit
y (%
)
Distance from the Nucleus (pm)
100 150 200 2505000
10
20
30
40
Orbital
90% probability offinding the electron
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We cannot know both the location and velocity of an electron (Heisenberg’s Uncertainty Principle), thus Schrodinger’s equation does not tell us the exact location of the electron, rather it describes the probability that an electron will be at a certain location in the atom. Here is an overview of electron properties:
1. Waves are confined to a space and can only have certain frequencies.
2. Electrons are considered waves confined to the space around an atomic nucleus. Electrons can only exist at specific frequencies. And according to E=hv (Planck’s hypothesis), these frequencies correspond to specific energies (or quantified amounts of energy.)
3. Electrons, like light waves, can be bent or diffracted.
Orbital
90% probability offinding the electron
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C. Heisenberg’s Uncertainty Principle says we cannot know both the location and the momentum of a particle.
A. When the radiation used to locate a particle hits that particle, it changes its momentum. Therefore, the position and momentum cannot both be measured exactly.
B. Today we say that the electrons are located in a region outside the nucleus called the electron cloud.
Werner Heisenberg
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Heisenberg Uncertainty PrincipleHeisenberg Uncertainty Principle Impossible to know both the velocity and
position of an electron at the same time
Microscope
Electron
Werner Heisenberg~1926
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I. Electron Cloud – Energy LevelsA.Electrons are found in various energy levels around the nucleus, analogous to the rungs of a ladder.
A. The lowest rung of the ladder corresponds to the lowest energy level.
B. A person can climb up or down a ladder by going from rung to rung. Similarly, an electron can jump from one energy level to another.
C. A person on a ladder cannot stand between the rungs; similarly, the electrons in an atom cannot exist between energy levels.
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A. Quantum: To move from one rung to another, a person climbing a ladder must move just the right distance. To move from one energy level to another, an electron must gain or lose just the right amount of energy. The exact amount of energy required to move from one energy level to another is called a quantum of energy.
B. Photon: When electrons move from one energy level to another energy level we see light – going from one energy level to another energy level gives off an exact amount of light (called a photon).
Electron Absorbing Energy (Photon)
Electron will move from a ground state to an excited state.
Electron Emitting Energy (Photon)
Electron will move from an excited state to a ground state.
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II. Quantum Mechanics Model of the Atom
Periodic Table with predicted ending electron configurations.
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Quantum Numbers
UPPER LEVEL
Four Quantum Numbers:Specify the “address” of each electron
in an atom
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
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Quantum Numbers
Principal Quantum NumberPrincipal Quantum Number ( nn )
Angular Momentum Quantum #Angular Momentum Quantum # ( ll )
Magnetic Quantum NumberMagnetic Quantum Number ( mmll )
Spin Quantum NumberSpin Quantum Number ( ms )
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A. Energy Levels: energy levels (represented by the letter n) are assigned values in order of increasing energy: n=1,2,3,4, and so forth…. which correspond to the periods in the periodic table. Which energy level is furthest away from the nucleus and has electrons with the highest energy - 1, 2, 3, or 4?
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Relative Sizes 1s and 2s
1s 2sZumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 334
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Energy level
Size of the orbital
n2 = # of orbitals in the energy level
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
1s
2s
3s
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B. Sublevels: Within each energy level, the electrons are located in various sublevels – there are 4 different sublevels s, p, d, and f. Sublevels define the shape of the orbital (s, p, d, & f).
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Shapes of s, p, and d-Orbitals
s orbital
p orbitals
d orbitals
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p-Orbitals
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 335
px pypz
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d-orbitals
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 336
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Atomic Orbitals
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Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
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s sublevel
p sublevel
d sublevel
f sublevel
1s 2s 2p 3p
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More pictures!
s pd f
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
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Orbitals combine to form a spherical
shape.
2s
2pz2py
2px
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
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Orbital (2 electrons/orbital)Orientation of orbital (px, py, pz)
Specifies the exact orbital within each sublevel
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
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Feeling overwhelmed?
Read chapter 4.2!
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
"Teacher, may I be excused? My brain is full."
Chemistry
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C. Orbitals: Where are the electrons in the various sublevels located in relation to the nucleus? Electrons are NOT confined to a fixed circular path, they are, however, found in definite regions of the atoms – these regions are called atomic orbital’s! Each orbital can only hold 2 electrons at a time (Pauli exclusion principle).
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Within the s sublevel there is only 1 orbital (which is spherical) it is called the s orbital.http://www.shef.ac.uk/chemistry/orbitron/AOs/1s/index.html
Within the p sublevel there are 3 orbital’s (which are dumbbell shaped) called the px, py, pz orbital’s.
Within the d sublevel there are 5 orbital’s (4 of which are cloverleaf shaped) called the dxy, dxz, dyz, dx2-y2, dz2 orbital’s.
Within the f sublevel there are 7 orbital’s - which are too complex to draw
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D. D. How many electrons can go into each energy level?
Each orbital can hold two electrons. (2n2 = number of electrons per energy level)
The 1st energy level (n=1) only has 1 sublevel called 1s. s only has 1 orbital called the s orbital, so only 2 electrons will be found in the 1st energy level. (2n2 = 2)
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The 2nd energy level (n=2) has 2 sublevels called 2s and 2p. s only has 1 orbital called the s orbital, p has 3 orbital’s called px, py, and pz orbitals, so 8 electrons will be found in the 2nd energy level. (2n2 = 8)
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The 3rd energy level (n=3) has 3 sublevels called 3s, 3p, and 3d. s only has 1 orbital called the s orbital, p has 3 orbital’s called px, py, and pz orbitals, and d has 5 orbital’s, so 18 electrons will be found in the 3rd energy level. (2n2 = 18)
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How about the 4th energy level?
It has 4 sublevels called 4s, 4p, 4d, and 4f. s only has 1 orbital, p has 3 orbital’s, d has 5 orbital’s, and f has 7 orbitals, so 32 electrons will be found in the 4th energy level. (2n2 = 32)
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E. Lets put it all together:
Example of neon atom:
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Spin of an electron within an orbital. Each orbital can hold two electrons, both with different spins (clockwise spin and counterclockwise spin). Electrons fill the orbitals one at a time with the same spin, then fill up the orbitals with electrons of the opposite spin.
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Spin Spin
An orbital can hold 2 electrons that spin in opposite directions.
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
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Copyright © 2006 Pearson Benjamin Cummings. All rights reserved.
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Quantum Numbers AnalogyEnergy Levels (n) or Principal Q.N.n=1 (Weir) n=2 (Liberty Hill) n=3 (Georgetown) n=4 (Austin)
Sublevels (l) or Azimuthal Q.N.l=0 – s shape 1 bedrooml=1 – p shape 3 bedrooml=2 – d shape 5 bedrooml=3 – f shape 7 bedroom
Orbitals (ml) or Magnetic Q.N.If l=0 then ml=0 (Represents the 1 bed/orbital in the s sublevel)If l=1 then ml= -1, 0, 1 (Represents the 3 bed’s/orbital’s in the p
sublevel) If l=2 then ml= -2, -1, 0, 1, 2 (Represents the 5 bed’s/orbital’s in the p
sublevel)If l=3 then ml= -3, -2, -1, 0, 1, 2, 3 (Represents the 7 bed’s/orbital’s in
the p sublevel)Magnetic Spin – Fourth Q.N. (ms)
ms = +1/2 - 1st electron in orbitalms = -1/2 – 2nd electron in orbital
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Level n 1 2 3
Sublevel l Orbital ml
Spin ms
0 0
0 0 1 0 -1 0 1 0 -1 2 1 0 -1 -2
2101
= +1/2
= -1/2
Allowed Sets of Quantum Numbers for Electrons in Atoms
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Maximum Number of Electrons In Each SublevelMaximum Number of Electrons In Each Sublevel
Maximum Number Sublevel Number of Orbitals of Electrons
s 1 2
p 3 6
d 5 10
f 7 14
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 146
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Quantum Numbers
n shell
l subshell
ml orbital
ms electron spin
1, 2, 3, 4, ...
0, 1, 2, ... n - 1
- l ... 0 ... +l
+1/2 and - 1/2
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Electrons In Atoms Notes (Chapter 4) Part 3 Electron
Configurations
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I. Electron Configuration: It should be obvious to you now that it is very difficult to draw a representation or model of atom showing where the electrons are located, so what we do instead is write electron configurations for elements.Definition of electron configuration: An electron configuration is a written representation of the arrangement of electrons in an atom.
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When constructing orbital diagrams and electron configurations, keep the following in mind:Aufbau Principle – electrons fill in order from lowest to highest energy.The Pauli Exclusion Principle – An orbital can only hold two electrons.Two electrons in the same orbital must have opposite spins.You must know how many electrons can be held by each angular momentum number, l. (ie; s can hold 2, 6 for p, l0 for d, 14 for f)Hund’s rule – the lowest energy configuration for an atom is the one having the maximum number of unpaired electrons for a set of degenerate orbitals. By convention, all unpaired electrons are represented as having parallel spins with spin “up”.
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Filling Rules for Electron Orbitals
Aufbau Principle: Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atom have been accounted for.
Pauli Exclusion Principle: An orbital can hold a maximum of two electrons.To occupy the same orbital, two electrons must spin in opposite directions.
Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results.
*Aufbau is German for “building up”
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Quantum Numbers
1. Principal # 2. Ang. Mom. # 3. Magnetic # 4. Spin #
energy level
sublevel (s,p,d,f)
orbital
electron
Pauli Exclusion PrinciplePauli Exclusion PrincipleNo two electrons in an atom can have the
same 4 quantum numbers.
Each electron has a unique “address”:
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Wolfgang Pauli
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II. What? How do we write an electron configuration?
A. 1st rule - electrons occupy orbitals that require the least amount of energy for the electron to stay there. So always follow the vertical rule (Aufbau Principle):
You notice, for example, that the 4s sublevel requires less energy than the 3d sublevel; therefore, the 4s orbital is filled with electrons before any electrons enter the 3d orbital!!!! (So just follow the periodic table and you can’t go wrong!!!!)
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II. What? How do we write an electron configuration?
1st rule - electrons occupy orbitals that require the least amount of energy for the electron to stay there. So always follow the vertical rule (Aufbau Principle):
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You notice, for example, that the 4s sublevel requires less energy than the 3d sublevel; therefore, the 4s orbital is filled with electrons before any electrons enter the 3d orbital!!!! (So just follow the chart and you can’t go wrong!!!!)
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B. 2nd rule – only 2 electrons can go into any orbital, however, you must place one electron into each orbital in a sublevel before a 2nd electron can occupy an orbital. Orbital’s with only 1 electron in the orbital are said to have an unpaired electron in them. (Hund’s rule)
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III. Writing Electron Configurations (3 ways): A. Orbital Notation: an unoccupied
orbital is represented by a line______, with the orbitals name written underneath the line. An orbital containing one electron is written as _____, an orbital with two electrons is written as ____. The lines are labeled with the principal quantum number and the sublevel letter.
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Examples: (Remember that you must place one electron into each orbital before a second
electron in placed into an orbital.)Hydrogen ____ Helium __
1s 1s
Lithium ___ ____
1s 2s
Carbon ____ ____ ____ ____ _____ 1s 2s 2px 2py 2pz
You try to write the notation for Titanium
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H = 1s1
1s
He = 1s2
1s
Li = 1s2 2s1
1s 2s
Be = 1s2 2s2
1s 2s
C = 1s2 2s2 2p2
1s 2s 2px 2py 2pz
S = 1s2 2s2 2p4
1s 2s 2px 2py 2pz 3s 3px 3py 3pz
THIS SLIDE IS ANIMATEDIN FILLING ORDER 2.PPT
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H = 1s1
1s
He = 1s2
1s
Be = 1s2 2s2
1s 2s
+1e-
+2e-
e-
+4e-
e-e-
e-
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B. Electron Configuration Notation: eliminates the lines and arrows of orbital notation. Instead, the number of electrons in a sublevel is shown by adding a superscript to the sublevel designation. The superscript indicates the number of electrons present in that sublevel.
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Examples:
Hydrogen: 1s1 Helium: 1s2
Lithium: 1s22s1
Carbon: 1s22s22p2
You try to write the notation for Titanium
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Fe = 1s1 2s22p63s23p64s23d6
1s 2s 2px 2py 2pz 3s 3px 3py 3pz
+26
e-
e-
e-
e-
4s 3d 3d 3d 3d
Iron has ___ electrons.26
3d
ArbitraryEnergy Scale
18
18
32
8
8
2
1s
2s 2p
3s 3p
4s 4p 3d
5s 5p 4d
6s 6p 5d 4f
NUCLEUS
e-
e-e-
e-
e- e-
e-
e-
e-
e-
e-
e-
e-e-
e-
e-
e-
e-
e- e-
e-
e-
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Orbital Filling
Element 1s 2s 2px 2py 2pz 3s Configuration
Orbital Filling
Element 1s 2s 2px 2py 2pz 3s Configuration
Electron ConfigurationsElectron
H
He
Li
C
N
O
F
Ne
Na
1s1
1s22s22p63s1
1s22s22p6
1s22s22p5
1s22s22p4
1s22s22p3
1s22s22p2
1s22s1
1s2
NOT CORRECTViolates Hund’s
Rule
Electron ConfigurationsElectron
H
He
Li
C
N
O
F
Ne
Na
1s1
1s22s22p63s1
1s22s22p6
1s22s22p5
1s22s22p4
1s22s22p3
1s22s22p2
1s22s1
1s2
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C. Short Hand or Noble Gas Notation: Use the noble gases that have complete inner energy levels and an outer energy level with complete s and p orbital’s. Use the noble gas that just precedes the element you are working with.
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Boron is ls22s22p1
The noble gas preceding Boron is He, so the short way is [He]2s22p1.
Sulfur is ls22s22p63s23p4
Short way: [Ne]3s23p4
Example: Titanium
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More Practice Problems: Write electron configurations for each of the following
atoms:1. boron2. sulfur3. vanadium4. iodineDraw orbital diagrams for these:5. sodium6. phosphorus7. chlorineWrite shorthand electron configuration for the following:8. Sr9. Mo 10. Ge
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Irregular Electron configurations – sometimes the electron configuration is NOT what we would predict it to be. Sometimes electrons are moved because (l) it will result in greater stability for that atom or (2) for some unknown reason??
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It is very important to define “stable” here. STABLE means:
1. all degenerate (equal energy) orbital’s are FULL
2. all degenerate orbital’s are half-full
3. all degenerate orbital’s are totally empty.
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Examples – draw the orbital’s (lines or boxes) and fill each orbital with the predicted number of electrons. Predict the electron configuration for Cr #24: [Ar]4s23d6
However, the real E. C. is [Ar]4s13d5. The 4s1 electron has been moved to achieve greater stability.
ALWAYS USE THE ACTUAL E. C. AND NOT THE PREDICTED ONE. YOU WILL HAVE THESE ATOMS WITH IRREGULAR E. C. HIGHLIGHTED OR MARKED ON YOUR PERIODIC TABLE.
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Electron configurations for Ions-First, determine if the element will lose or gain electrons. Secondly, what number of electrons will be gained or lost? It is recommended that you write the e.c. for the atom and then determine what will happen.
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For cations (positive ions) – look at the element and decide how many electrons will be lost when it ionizes and keep that in mind when writing the E. C. The last number in the E. C. will now be LESS than what is written on your periodic table.Ex. Write the electron configuration for magnesium ion: [Ne]3s2 is for the atom. Mg is a metal and will lose its valence (outer) electrons, so the e.c. for Mg2+ is 1s22s22p6
Practice: 1. #32. #123. #194. #13
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For anions (negative ions) – look at the element and decide how many electrons that element will GAIN when it ionizes. The last number in the E. C. will be MORE than what is written on the periodic table.Ex. Sulfide ion: Sulfur atom is 1s22s22p4. Sulfur is a nonmetal with 6 valence electrons (2s2 and 2p4) and will gain 2 electrons: 1s22s22p6 is for the sulfide ion.Practice:
1. #172. #73. #164. #30