energy unit learning goal 2: examine the placement of electrons in orbitals
TRANSCRIPT
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Bohr’s Atomic Model
1. Atom has small positive nucleus.2. Electrons orbit like planets orbit the sun.
3. Electrons orbit in certain allowed energy levels.4. Electrons can jump to different orbits but only by absorbing or emitting a photon of light with the correct energy content.
Good start but some basic problems:Electrons do not “orbit” in circular paths.
Could not explain why negative electrons didn’t get attracted into the nucleus
This model only worked for Hydrogen
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DeBroglie & the Wave Mechanical Model of the Atom
DeBroglie & Schrodinger suggested that electrons exhibited both wave and particle characteristics.
This is referred to the wave/particle
duality Schrodinger came up with a model (wave mechanical model) that worked with atoms in addition to hydrogen.
Wave Mechanical Model
• Electron states are described as orbitals.• Electrons are more like fireflies than planets.– An orbital is described as the probability map of
an electron’s motion.
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Orbitals vs. Orbits
Orbitals are nothing like orbits.To picture orbitals, imagine a single male firefly in a room. In the center of the room is a vial of nectar.
The room is dark with a camera with an open shutter in the corner.The developed picture will look something the diagram to the left.
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Suppose while watching the room, you see a flash here.
XWhere will the firefly flash next?
There’s no way of really knowing, but the likely-hood is that it will flash where the “film” had the densest concentration of flashes.
Shrodinger’s model cannot predict the
path of the electron, but can predict the
probability of find the electron in a certain
region.
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The first quantum number: n
Describes the energy level
n = 1, 2, 3, 4, etc.
Notice how the rows are numbered on the periodic table!
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Sublevels
The principle energy levels are divided into sublevels. The second quantum number describes the shape of these sublevels.
l = 0, 1, 2, 3, 4, 5, 6, 7
However, we rarely refer to these sublevels by number. We usually use a letter:
s p d f
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Notice the energy level determines the # of sublevels!
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Principle Energy Levels
• Discrete Energy levels that are labeled with integers.– 1, 2, 3, 4, 5, 6, 7.
• Sublevels– Each Principle Energy Level is subdivided into
sublevels and labeled with a letter.• s (holds 2 e- )• p (holds 6 e- ) • d (holds 10 e- ) • f (holds 14 e- ) • The letters tell the shape of the orbital.
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Shapes of Sublevels
Every energy level has an s sublevel. The only difference being the diameter!
s sublevels are “spherical” in shape.
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The p sublevels are dumbell shaped and are made of 3 orbitals or “lobes”.Each orbital can hold 2 electrons.
p sublevels are found on energy levels 2 or greater
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The d sublevels are four-petaled and are made of 5 orbitals or “lobes”.Each orbital can hold 2 electrons.
d sublevels are found on energy levels 3 or greater
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The f sublevels are made of 7 orbitals or “lobes”.
Each orbital can hold 2 electrons.
f sublevels are found on energy levels 4 or greater
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Summary ....so far
sublevel # orbitals # electrons
s
p
d
f
1
3
5
7
2
6
10
14
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Pauli Exclusion Principle:
• An atomic orbital can hold a maximum of two electrons, and those two electrons must have opposite spin.
Now let’s put it all together.....
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H
H
1s1s1
He
He1s
He has 2 electrons 1s2
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H
H
1s1
He
He1s
has 3 electrons
1s2
Li
Li1s 2s
1s22s1
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H He
has 4 electrons
Li
Li1s 2s
1s22s1
Be
Be2s1s
1s22s2
B
B
2s1s 2p1s22s22p1
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H He
Li Be B
C2s1s 2p
1s22s22p2
Li1s 2s
1s22s1
Be 1s 2s1s22s2
B2p 1s22s22p1
1s 2s
C
Stop! Before adding the next electron, we have to know about Hund’s Rule:
Hund’s Rule: we put 1 electron in each orbital
before we pair them up!
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H He
Li Be B
C
1s22s22p3
B2p 1s22s22p1
1s 2s
C N
N2s1s 2p
1s22s22p22p1s 2s
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H He
Li Be B
C
1s22s22p4
B2p 1s22s22p1
1s 2s
C N
1s22s22p2
O2s1s 2p
2p1s 2s
N 2p1s 2s1s22s22p3
O
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H He
Li Be B
C
1s22s22p5
C N
1s22s22p22p1s 2s
N 2p1s 2s1s22s22p3
F2s1s 2p
O F
O 2p1s 2s1s22s22p4
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H He
Li Be B
1s22s22p6
C N
N 2p1s 2s1s22s22p3
O F
O 2p1s 2s1s22s22p4
Ne2s1s 2p
F 2p1s 2s1s22s22p5
Ne
This is a very important arrangement! With 8 electrons in the valence shell, we have a stable octet. Notice neon is a noble gas, very inert, and is at the end of its row!
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H He
O
1s22s22p63s1
1s22s22p42p1s 2s
F 2p1s 2s1s22s22p5
Ne 2p1s 2s1s22s22p6
Li Be B C N O F NeNa
Na2s1s 2p 3s
[Ne] 3s1
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H He
Na [Ne] 3s[Ne] 3s1
Li Be B C N O F NeNa
Mg [Ne]3s
[Ne] 3s2
Ne 2p1s 2s 1s22s22p6
Mg
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H He
Na [Ne] 3s[Ne] 3s1
Li Be B C N O F NeNa Mg
[Ne] 3s23p1
Ne 2p1s 2s 1s22s22p6
Al
Mg [Ne] 3s[Ne] 3s2
Al [Ne]3s 3p
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H He
Li Be B C N O F NeNa Mg Al
[Ne] 3s23p2
3p
Si
Al [Ne] 3s[Ne] 3s23p1
Si [Ne]3s 3p
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H He
Li Be B C N O F NeNa Mg Al Si
[Ne] 3s23p3
3p
P
Al [Ne] 3s[Ne] 3s23p1
3pSi [Ne] 3s[Ne] 3s23p2
P[Ne]3s 3p
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H He
Li Be B C N O F NeNa Mg Al Si P
3p
S
Al [Ne] 3s[Ne] 3s23p1
3pSi [Ne] 3s[Ne] 3s23p2
S[Ne]3s 3p
3pP [Ne] 3s[Ne] 3s23p3
[Ne] 3s23p4
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl
3pP [Ne] 3s[Ne] 3s23p3
Cl[Ne]3s 3p
[Ne] 3s23p5
3pS [Ne] 3s[Ne] 3s23p4
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
3pP [Ne] 3s[Ne] 3s23p3
[Ne] 3s23p6
3pS [Ne] 3s[Ne] 3s23p4
Ar[Ne]3s 3p
3pCl [Ne] 3s[Ne] 3s23p5
Another Noble gas with a stable octet!
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl ArK
[Ar] 4s1K[Ar]4s
3pAr [Ne] 3s[Ne] 3s23p6
Notice that we have started filling the 4th energy level before even starting the 3d!
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
Ca
[Ar] 4s2Ca[Ar]4s
K [Ar] 4s[Ar] 4s1
K
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
Sc
[Ar] 4s23d1
K [Ar] 4s[Ar] 4s1
K Ca
Ca [Ar] 4s[Ar] 4s2
3dSc[Ar]
4s
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
Ti
[Ar] 4s23d2
K [Ar] 4s[Ar] 4s1
K Ca Sc
Ca [Ar] 4s[Ar] 4s2
Sc [Ar] 4s[Ar] 4s23d1
3d
3dTi[Ar]
4s
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
V
[Ar] 4s23d3
K Ca Sc Ti
Ti [Ar] 4s[Ar] 4s23d2
3d
Sc [Ar] [Ar] 4s23d13d4s
3dV[Ar]
4s
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
Cr
[Ar] 4s23d4
K Ca Sc Ti V
Ti [Ar] 4s[Ar] 4s23d2
3d
Sc [Ar] [Ar] 4s23d13d4s
V [Ar] [Ar] 4s23d33d4s
3dCr[Ar]
4s
Stop! Chromium is a stealer!
A more stable arrangement is formed when all orbitals are half-filled than one full & one empty
[Ar] 4s13d5
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
Mn
[Ar] 4s23d5
K Ca Sc Ti V Cr
Ti [Ar] 4s [Ar] 4s23d23d
V [Ar] [Ar] 4s23d33d4s
3dMn[Ar]
4s
Cr [Ar] 4s[Ar] 4s13d5
3d
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H He
Li Be B C N O F NeNa Mg Al Si P S Cl Ar
Cu
[Ar] 4s23d9
K Ca Sc Ti V Cr Mn Fe Co Ni
3dCu[Ar]
4s
Copper (and all in this column) steal an electron from the 4s orbital to fill
its 3d![Ar] 4s13d10
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Zn
H He
Li Be B C N O F NeNa Mg Al Si P S Cl ArK Ca Sc Ti V Cr Mn Fe Co Ni Cu
Cu [Ar] 4s[Ar] 4s13d10
3d
[Ar] 4s23d10
3dZn[Ar]
4s
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