atomic emission spectra
DESCRIPTION
Atomic Emission Spectra. Zumdahl 2 : p. 290-299. Atoms. Let go. A range. What is light?. White light: reflection of all colors Black light: absorption of all colors Colors are each a different wavelength (λ: lamda) of light. Colors - PowerPoint PPT PresentationTRANSCRIPT
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Atomic Emission SpectraAtomic Emission Spectra
Zumdahl2: p. 290-299
Ato
ms
Ato
ms
Let g
oLe
t go
A
A
rang
era
ng
e
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What is light?
White light: reflection of all colorsBlack light: absorption of all colorsColors are each a different
wavelength (λ: lamda) of light
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Colors Different wavelengths of light are seen
as different colors. Different colors indicate (show) different
energy levels.
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c=fc=fλ λ (velocity of light = frequency x wavelength)
the greater the frequency the shorter the wavelength
ΔE = hfΔE = hf (energy lost by the electron = h(constant) x frequency
Frequency (and thus, color) of the light depends on the amount of energy lost by the electron.
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c=fc=fλλ
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When atoms are “exited” (energy is added) they produce light.
Not white or all-colored light, but one color at a time.
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Study the light emitted (produced) by atoms and ions to deduce (find out) the structure of atoms.
When an atom is “excited” its electrons gain energy and move to a higher energy level. To return to a lower energy level, electrons must lose energy. They do this by giving off light.
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Continuous spectrum:Continuous spectrum: all wavelengths of visible light contained in white light.
Light emitted by an atom can be separated into a line spectrumline spectrum that shows exactly what frequencies of light are present.
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Closer to nucleus
Further from nucleus
Increasin
g frequ
ency
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Because the light emitted from atoms is a line spectrumline spectrum (not a continuous spectrum) we determine that:
There are “discrete” (separate) energy energy levelslevels for each atom that can only produce light of certain wavelengths (this is NOT ordinary white light!).
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Increasing frequency (f) (increasing energy)
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Increasing frequency (f) (increasing energy)
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Hydrogen
Only certain energy levels can occur (not a continuous spectrum)
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Energy Level Diagram
The larger the difference in energy, the greater the frequency (thus, the more purple the light).
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Increasing potential energy
Frequency
Visible
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convergence:convergence: the lines in a spectrum converge (get closer together) as frequency increases. related to how much energy is required
to remove the electron from the atom (ionize)
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Closer to nucleus
Further from nucleus
Increasin
g frequ
ency
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Stop
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Electronic StructureElectronic Structure
Energy LevelsShells
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Most stable = closest to nucleus
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1st energy level = 2
2nd energy level = 8
Electronic structure: number of electrons in each orbital
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H=1O=2,6 (two electrons in the first
energy level, six in the second)Al=2,8,3Cl=Ca=
Different isotopes have the same electronic structure and the same chemical properties!
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Electron BehaviorElectron BehaviorValence shell: outer shell of an atom
determine the physical and chemical properties of an atom
Valence Shell
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How many electrons in valence shell? Al Ne Li Ca
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Stop here
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HL TopicHL Topic
Electronic Structure of AtomsElectronic Structure of AtomsZumdahl2: p. 307-312
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Electronic Structure
I. Energy levelsA. Sub-levels
1. Orbitala. Spin
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Energy Levels
Major shells (layers) around the nucleus filled before higher levels are filled 1st: 2 electrons 2nd: 8 electrons 3rd: 8 electrons
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Sub-levelsDifferent shapess – sphere
one orbitalp – figure eight
three orbitalsd –
five orbitalsf –
seven orbitals
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p Sub-level
p sub-level has three orbitalspx, py, pz
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d and f sub-levels have very complex shapes
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Orbitals
Each orbital can hold two electrons.Electrons spin in opposite directions
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Energy Level
Types of sub-
levels
Total orbits
Electron capacity
1 s 1 2
2 s, p 1+3=4
8
3 s, p, d 1+3+5=9
18
4 s, p, d, f 1+3+5+7=16
2
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Energies of sub-levels
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Electronic structure of atoms
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Energy States
Depending on where an electron was around the nucleus, it had different energy states.
Ground state: An orbit near the nucleus: not very exited at all.
Excited State: An orbit farther awayfrom the nucleus: much morepotential for giving off energy.
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Heisenberg Uncertainty Principle
If electrons are both waves and particles, where are they around the atom?
It is impossible to figure out both the position and velocity of an electron, at the same time.
We CAN figure out the probability that an electron is in any one spot at any given time.
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Electron Configuration
The arrangement of electrons in an atom Each element’s atoms are different Arrangement with the lowest energy=
ground state electron configurationHow do we figure out what the
ground state electron configuration looks like?
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How do we figure out where the electrons are?
1. Figure out the energy levels of the orbitals
2. Add electrons to the orbitals according to three rules
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1: Aufbau Principle1: Aufbau Principle
An electron goes to the lowest-energy orbital that can take it.
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2: Pauli Exclusion Principle
No two electrons can have exactly the same configuration description Can have the same orbital, but must
have opposite spins.
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3. Hund’s RuleOrbitals of equal energy are each
occupied by one electron before any orbital is occupied by a second electron
All electrons that are by themselves in an orbit must have the same spin.
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Electron configuration: the arrangement of electrons in an atom.
So…what do we do with this information?!
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How do we write electron configurations?
Electron Configuration NotationOrbital NotationNoble Gas Notation (shorthand)
All ways to communicate where the electrons are in the ground state of any atom.
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s – sphere one orbital – 2 electrons
p – figure eight three orbitals – 6 electrons
d – five orbitals – 10 electrons
f – seven orbitals – 14 electrons
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Orbital Notation
Electron configuration goes below a line or box
Arrows representing electrons go on the lines or in the boxes
1s 2s 2p 3s 3p 4s
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Fluorine? 9 electrons
Magnesium? 12 electrons1s 2s 2p 3s 3p 4s
1s 2s 2p 3s 3p 4s
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Electron Configuration NotationMain energy level Sub-levelElectrons
Carbon (6 electrons) 1s22s22p2
Aluminum (13 electrons) 1s22s22p63s23p1
OxygenArgonCopper
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Orbital Notation
Boron1s22s22p1
Atomic Number?How many electrons?Orbital notation
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Aufbau Principle: start with 1s and work up in energy level
Pauli Exclusion Principle: No two elements can have the same arrangement of electrons
Hund’s Rule: Fill in one electron per orbital first, then go back.
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Orbital Notation
Nitrogen1s22s22p3
Atomic Number?Number of Electrons?Orbital Notation?
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Practice
Write the orbital notation for:FluorineAluminumCarbonOxygen
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Practice
Write the electron configuration notation of:
Be (Beryllium)N (Nitrogen)Si (Silicon)Na (Sodium)
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Noble Gas Notation (Shorthand)
Noble gasses have totally filled outer orbitals.
If Ne (a noble gas) is 1s22s22p6, we can abbreviate Na as [Ne]3s1.
Sodium has one more electron than Neon, so its Noble Gas Notation is Neon plus one electron in the s sublevel of the third energy level.
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Practice
Fe Electron Configuration Notation Noble Gas Notation
K Electron Configuration Notation Noble Gas Notation
LiBe
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