Electron Orbitals Cartoon courtesy of lab-initio.com

The Bohr Model of the Atom I pictured electrons orbiting the nucleus much like planets orbiting the sun. But I was wrong! They’re more like bees around a hive. Neils Bohr

Quantum Mechanical Model of the Atom Mathematical laws can identify the regions outside of the nucleus where electrons are most likely to be found. These laws are beyond the scope of this class…

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

Quantum numbers Numbers that specify the properties of atomic orbitals and electrons. They indicate the region occupied by an orbital in terms of: Distance from the nucleus Orbital shape Position with respect to the 3-D x, y, z axis

Electron Energy Level (Shell) Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. “n” is also known as the Principle Quantum number. As “n” increases the radius increases.

Orbital qunatum number (SUBSHELL) Generally symbolized by l, it is a measure of orbital angular momentum, which indicates the shape of the orbital.

Magnetic quantum number Generally symbolized by ml, in indicates the orbital around the 3 axes in space (orientation in space) s = 1 orientation p = 3 orientations d = 5 orientations f = 7 orientations Identifies the specific orbital.

Spin Quantum number Generally symbolized by ms, it tells the electrons spin on its axis. Clockwise or counterclockwise Whether bound or free all electrons spin.

Electron Orbitals An orbital is a region within an energy level where there is a probability of finding an electron. Orbital shapes are defined as the surface that contains 90% of the total electron probability.

s p d f There are four shapes or sublevels: Each sublevel has “orientations” or orbitals around the origin of the x-y-z axis. Take a look!

s Orbital shape The s orbital has a spherical shape centered around the origin of the three axes in space.

S = Shaped like a sphere 1) 3s 2) 3) No matter which way you turn it in space, it will always be a sphere so there are no separate orbitals (orientations in space). X Z Y X Y Z 3s 2s 1s Z Y X 2) It exists on every energy level. Level 2’s S sublevel is big enough to encompass Level 1’s and Level 3’s encompasses them both, like nesting dolls. Again, a sphere! Still a sphere! 3) No matter how big ‘s’ is, it only can hold 2 electrons, max!

p orbital shape There are three dumbbell-shaped p orbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.

P = Dumb Bell shape px py pz 1) 2) 3) 2e- The ‘p’ sublevel is made up of 3 orbitals or ‘orientations’ in space. Y px When it lies along the x-axis 2e- py When it lies along the y-axis X pz 2e- When it lies along the z-axis Z 2) Each orientation or orbital can hold 2 electrons max for a total of 6 electrons. 3) The ‘p’ sublevel is first found on Principle Energy Level 2. Like ‘s’, it increases in size with each increase in energy level.

d orbital shapes Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of “double dumbells” …and a “dumbell with a donut”!

Shape of f orbitals

Energy Levels, Orbitals, Electrons Orbital type in the energy level (types = n) Number of orbitals Electrons electrons per Energy level (2n2) 1 s 2 p 3 6 8 d 5 10 18 4 f 7 14 32

Orbital filling table

Electron configuration of the elements of the first three series

Each element can be represented by its **Electron Configuration** How does this work, anyway? Each element can be represented by its **Electron Configuration** for example: The superscript tells how many electrons are in that sublevel. Carbon (C) is 1s2 2s2 2p2 The coefficient shows what level from the nucleus. This is known as the Principle Quantum Number. The letter s,p,d or f, represents the shape of the sublevel. This is known as the Orbital Quantum Number.

1s22s22p2 2 2 So tells us that Carbon has: There are 4 electrons total in the valence shell. These are the valence electrons. So 1s22s22p2 tells us that Carbon has: 2 2 2 electrons in the ‘s’ sublevel (the sphere) on principle energy level ‘1’ The outermost energy level is ‘2’ for Carbon. This is its valence shell. 2 electrons in the ‘s’ sublevel (the sphere) on principle energy level ‘2’ 2 electrons in the ‘p’ sublevel (the dumb bell) on principle energy level ‘2’

Creating Electron Configurations STUDY for the PT QUIZ (all required elements) Creating Electron Configurations The right side is known as the “p” block It starts with the periodic table: The transition metals are known as the “d” block The first two columns, and “He” are called the “s” bock. The bottom two rows, called the rare earth elements or Lanthanide and Actinide series make up the “f” block.

Electron Spin Electron spin describes the behavior (direction of spin) of an electron within a magnetic field. Possibilities for electron spin: Clockwise Counterclockwise

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

A. General Rules Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins. 2 P’s in a Pod

A. General Rules Aufbau Principle aufBAU Electrons fill the lowest energy orbitals first. “Lazy Tenant Rule” aufBAU

WRONG RIGHT A. General Rules Hund’s Rule Within a sublevel, place one e- per orbital before pairing them. “Empty Bus Seat Rule” or Hand’s Rule WRONG RIGHT

Example 1 ___ ___ ___ 4p ___ ___ ___ ___ ___ 3d ___ 4s 3p 3s ___ ___ ___ 4p ___ ___ ___ ___ ___ 3d ___ 4s 3p 3s 2p 2s 1s Example of Si, Z=14 *Hint #1: The “Z” number refers to the Atomic Number which is the number of protons AS WELL AS electrons.

Example 2- You Try ___ ___ ___ 4p ___ ___ ___ ___ ___ 3d ___ 4s 3p 3s ___ ___ ___ 4p ___ ___ ___ ___ ___ 3d ___ 4s 3p 3s 2p 2s 1s Example 2- You Try Example of Ti, Z=22 *Hint #1: The “Z” number refers to the Atomic Number which is the number of protons AS WELL AS electrons.

You Try These Mg Cl Co Br

O Z=8 1s2 2s2 2p4 BUILDING AN ELECTRON CONFIGURATION (click the mouse to start an example) Principle Energy Level 4 4s 3px 3py 3pz 4d 4d 4d 4d 4d 3 3s 3px 3py 3pz 3d 3d 3d 3d 3d 2 O Z=8 2s 2px 2py 2pz 1 1s2 2s2 2p4 1s nucleus

Ne Z=10 1s2 2s2 2p6 BUILDING AN ELECTRON CONFIGURATION (click the mouse to start an example) Principle Energy Level 4 4s 3px 3py 3pz 4d 4d 4d 4d 4d 3 3s 3px 3py 3pz 3d 3d 3d 3d 3d 2 Ne Z=10 2s 2px 2py 2pz 1 1s2 2s2 2p6 1s nucleus

P Z=15 1s2 2s2 2p6 3s2 3p3 BUILDING AN ELECTRON CONFIGURATION (click the mouse to start an example) Principle Energy Level 4 4s 3px 3py 3pz 4d 4d 4d 4d 4d 3 3s 3px 3py 3pz 3d 3d 3d 3d 3d P Z=15 2 2px 2py 2pz 2s 1 1s2 2s2 2p6 3s2 3p3 1s nucleus 2 + 2 + 6 + 2 + 3 = 15

K Z=19 2 1s2 2s 2p6 3s 3p6 4s1 BUILDING AN ELECTRON CONFIGURATION (click the mouse to start an example) Principle Energy Level 4 4s 3px 3py 3pz 4d 4d 4d 4d 4d 3 3s 3px 3py 3pz 3d 3d 3d 3d 3d K Z=19 2 2px 2py 2pz 2s 1 2 2 1s2 2s 2p6 3s 3p6 1s 4s1 nucleus 2 + 2 + 6 + 2 + 6 +1 = 19

Element Configuration notation Orbital notation Noble gas Lithium 1s22s1 ____ ____ ____ ____ ____ 1s 2s 2p [He]2s1 Beryllium 1s22s2 [He]2s2 Boron 1s22s22p1 [He]2s2p1 Carbon 1s22s22p2 [He]2s2p2 Nitrogen 1s22s22p3 1s 2s 2p [He]2s2p3 Oxygen 1s22s22p4 [He]2s2p4 Fluorine 1s22s22p5 [He]2s2p5 Neon 1s22s22p6 [He]2s2p6

Energy level (shell) = floor Subshell = room Orbital = love seat Analogy Electron Cloud = dorm Energy level (shell) = floor Subshell = room Orbital = love seat Spin = each person