Energy Unit Learning Goal 2: Examine the Placement of Electrons in Orbitals.

1. Atom has small positive nucleus.
Bohr’s Atomic Model 1. Atom has small positive nucleus. Good start but some basic problems: 2. Electrons orbit like planets orbit the sun. Electrons do not “orbit” in circular paths. 3. Electrons orbit in certain allowed energy levels. Could not explain why negative electrons didn’t get attracted into the nucleus 4. Electrons can jump to different orbits but only by absorbing or emitting a photon of light with the correct energy content. This model only worked for Hydrogen Copyright © by McDougal Littell. All rights reserved.

Schrodinger Wave Equation
Equation for probability of a single electron being found along a single axis (x-axis) Erwin Schrodinger

Heisenberg Uncertainty Principle
“One cannot simultaneously determine both the position and momentum of an electron.” You can find out where the electron is, but not where it is going. OR… You can find out where the electron is going, but not where it is! Werner Heisenberg

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. Copyright © by McDougal Littell. All rights reserved.

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.

Orbitals are nothing like orbits.
Orbitals vs. Orbits Orbitals are nothing like orbits. An orbit is a defined path and an orbital is a probability map. 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. Copyright © by McDougal Littell. All rights reserved.

Electron Energy Level (Shell)
Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. Number of electrons that can fit in a shell: 2n2

An orbital is a region within an energy level where there is a probability of finding an electron. This is a probability diagram for the s orbital in the first energy level… Orbital shapes are defined as the surface that contains 90% of the total electron probability.

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! Copyright © by McDougal Littell. All rights reserved.

Energy Levels, Sublevels, Electrons
Sublevels in main energy level (n sublevels) Number of orbitals per sublevel Electrons per sublevel electrons per level (2n2) 1 s 2 p 3 6 8 d 5 10 18 4 f 7 14 32

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.

s sublevels are “spherical” in shape.
Shapes of Sublevels s sublevels are “spherical” in shape. Every energy level has an s sublevel. The only difference being the diameter! Copyright © by McDougal Littell. All rights reserved.

Each orbital can hold 2 electrons.
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 Copyright © by McDougal Littell. All rights reserved.

Each orbital can hold 2 electrons.
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 Copyright © by McDougal Littell. All rights reserved.

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 Copyright © by McDougal Littell. All rights reserved.

Orbital filling table

Pauli Exclusion Principle
Two electrons occupying the same orbital must have opposite spins Wolfgang Pauli

Electron configuration of the elements of the first three series

Element Configuration notation Orbital notation Noble gas
Lithium 1s22s1 ____ ____ ____ ____ ____ 1s s p [He]2s1 Beryllium 1s22s2 [He]2s2 Boron 1s22s2p1 [He]2s2p1 Carbon 1s22s2p2 [He]2s2p2 Nitrogen 1s22s2p3 1s s p [He]2s2p3 Oxygen 1s22s2p4 [He]2s2p4 Fluorine 1s22s2p5 [He]2s2p5 Neon 1s22s2p6 [He]2s2p6

Irregular conformations of Cr and Cu
Chromium steals a 4s electron to half fill its 3d sublevel Copper steals a 4s electron to FILL its 3d sublevel

Notice the # of columns in each group!
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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! Li 1s 2s 1s22s1 Be 1s22s2 B 2p 1s22s22p1 C 2s 1s 2p 1s22s22p2 1 2 3 4 5 6 7 H He C Li Be B Copyright © by McDougal Littell. All rights reserved.

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! 1s22s22p3 N 1s 2s 2p 1s22s22p4 O 1s 2s 2p 1s22s22p5 F 1s 2s 2p 1s22s22p6 Ne 2s 1s 2p 1 2 3 4 5 6 7 H He Ne Li Be B C N O F Copyright © by McDougal Littell. All rights reserved.

[Ne] 3s23p1 Al [Ne] 3s 3p [Ne] 3s23p2 Si [Ne] 3s 3p [Ne] 3s23p3 P [Ne] 3s 3p S[Ne] 3s 3p [Ne] 3s23p4 1 2 3 4 5 6 7 H He Li Be B C N O F Ne S Na Mg Al Si P Copyright © by McDougal Littell. All rights reserved.

[Ne] 3s23p3 P [Ne] 3s 3p [Ne] 3s23p4 S [Ne] 3s 3p [Ne] 3s23p5 Cl [Ne] 3s 3p Ar[Ne] 3s 3p [Ne] 3s23p6 Another Noble gas with a stable octet! 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Ar Na Mg Al Si P S Cl Copyright © by McDougal Littell. All rights reserved.

[Ne] 3s23p6 Ar [Ne] 3s 3p Notice that we have started filling the 4th energy level before even starting the 3d! K[Ar] 4s [Ar] 4s1 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Copyright © by McDougal Littell. All rights reserved.

[Ar] 4s1 K [Ar] 4s [Ar] 4s2 Ca [Ar] 4s [Ar] 4s23d1 Sc [Ar] 4s 3d [Ar] 4s23d2 3d Ti[Ar] 4s 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar Ti K Ca Sc Copyright © by McDougal Littell. All rights reserved.

Sc [Ar] [Ar] 4s23d1 4s 3d [Ar] 4s23d2 Ti [Ar] 4s 3d [Ar] 4s23d3 3d V[Ar] 4s 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar V K Ca Sc Ti Copyright © by McDougal Littell. All rights reserved.

Stop! Chromium is a stealer!
A more stable arrangement is formed when all orbitals are half-filled than one full & one empty Sc [Ar] Stop! Chromium is a stealer! [Ar] 4s23d1 4s 3d [Ar] 4s23d2 Ti [Ar] 4s 3d V [Ar] [Ar] 4s23d3 4s 3d 3d Cr[Ar] 4s [Ar] 4s13d5 [Ar] 4s23d4 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar Cr K Ca Sc Ti V Copyright © by McDougal Littell. All rights reserved.

Ti [Ar] [Ar] 4s23d2 4s 3d V [Ar] [Ar] 4s23d3 4s 3d [Ar] 4s13d5 Cr [Ar] 4s 3d 3d Mn[Ar] 4s [Ar] 4s23d5 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar Mn K Ca Sc Ti V Cr Copyright © by McDougal Littell. All rights reserved.

Copper (and all in this column) steal an electron from the 4s orbital to fill its 3d! 3d Cu[Ar] 4s [Ar] 4s23d9 [Ar] 4s13d10 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar Cu K Ca Sc Ti V Cr Mn Fe Co Ni Copyright © by McDougal Littell. All rights reserved.

[Ar] 4s13d10 Cu [Ar] 4s 3d [Ar] 4s23d10 Zn[Ar] 4s 3d [Ar] 4s23d104p1 3d Ga[Ar] 4s 4p 1 2 3 4 5 6 7 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Copyright © by McDougal Littell. All rights reserved.

Energy Unit Learning Goal 2: Examine the Placement of Electrons in Orbitals.

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