honors chemistry chapter 5

Honors Chemistry Chapter Honors Chemistry Chapter 55

Electrons

“The more success the quantum theory has, the sillier it looks.”

~Albert Einstein, Nobel Prize in Physics, 1921.

“Quantum mechanics: the dreams that stuff is made of.” ~unknown

“If quantum mechanics has not yet profoundly shocked you, you have not yet understood it.”

~Niels Bohr, Nobel Prize in Physics, 1922.

Where are electrons located?• Outside the nucleus

• How are they arranged?

Bohr model of electron Bohr model of electron placementplacement

Called the “planetary” modelCalled the “planetary” model Electrons closer to the nucleus – Electrons closer to the nucleus –

lower “energy level”lower “energy level” Electrons farther away from the Electrons farther away from the

nucleus – higher “energy level”nucleus – higher “energy level”

Called the “shells” K, L, M, NCalled the “shells” K, L, M, N 2, 8, 18, 32 electrons2, 8, 18, 32 electrons Studied the emission spectrum of Studied the emission spectrum of

HydrogenHydrogen Specific colors that are emitted Specific colors that are emitted

(given off) when an atom releases (given off) when an atom releases energyenergy

Quantum Staircase

An electron in a stable orbit will have a specific, restricted (quantitized) energy:

Niels Bohr

Max Planck

• Stated that the object (metal) emits energy in small, specific amounts called Quanta.

• Quantum is the minimum quantity of energy that can be lost or gained by an atom.

• Step ladder analogy

Albert Einstein

Took Planck’s idea a little further.

He introduced that electromagnetic radiation has a dual wave-particle nature.Light exhibits many wavelike

propertiesCan also be thought of as a

stream of particles

• Two important concepts from Bohr:

• Electrons exist only in certain discrete energy levels

• Energy is involved in moving an electron from one level to another

• IN REALITY, ELECTRONS DO NOT ORBIT THE NUCLEUS LIKE PLANETS ORBITING A STAR!!!!

Bohr’s Model

• Electrons not really in “planetary” orbits

• Are really in areas of “probability” called “electron clouds”

• Quantum Model of electron placement

Quantum Mechanical Model

• This model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus

• Heisenburg’s Uncertainty Principle

– it is not possible to know both the velocity and position of a particle at the same time

– velocity = speed and direction

Orbital - 3 dimensional region around the nucleus where a particular electron can be located “clouds” - that show a region of

high probability of finding an electron

size and shape of “cloud” depends on energies of electrons that occupy them

Principal Energy LevelsPrincipal Energy Levels

Indicates main energy Indicates main energy level of an electron in an level of an electron in an atomatom

called “shells”called “shells”1 = lowest 7 = highest1 = lowest 7 = highestcan be any positive can be any positive

integerinteger

Sublevel

• Indicates the shape of an orbital

labeled s, p, d, f

s = spheres = spherep = dumbbell or figure-p = dumbbell or figure-

eighteightd = 4 lobesd = 4 lobesf = complicatedf = complicated

• Orbital shapes for Sc

• funky orbitals

Principal Energy Levels

Are divided into sublevels the number of sublevels allowed is equal

to the principal energy level (n) (up to n=4) PEL = 1 1 sublevel PEL = 2 2 sublevels PEL = 3 3 sublevels PEL = 4 4 sublevels

Wish you were here?Well, you’re not, so pay attention!

““s” sublevel – 1 orbital alloweds” sublevel – 1 orbital allowed““p” sublevel – 3 orbitals allowedp” sublevel – 3 orbitals allowed““d” sublevel – 5 orbitals allowedd” sublevel – 5 orbitals allowed““f” sublevel – 7 orbitals allowedf” sublevel – 7 orbitals allowed

PELPEL sublevels allowedsublevels allowed

11 ss

22 s, ps, p

33 s, p, ds, p, d

44 s, p, d, fs, p, d, f

Each sublevel has a certain number of orbitals allowed

Sublevel orbitals allowed

s 1

p 3

d 5

f 7

• Maximum of 2 e- in any orbital !

• They “spin” in opposite directions

WAKE UP!!!!!!!!

Don’t give up!

You can’t escape!

I know you’d rather be here, I know you’d rather be here, but it gets better, I promise!but it gets better, I promise!

Are you ready????????

• Chart that follows this slide:

•Principal energy level•type of sublevel•#orbitals per type•#orbitals per level•Max. # electrons

Principal Energy Level (pel)

Type of sublevel

# orbitals per type of sublevel

# orbitals per pel

n2

Maximum number of electrons per

pel 2n2

1 s 1 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 32

Rules for writing electron configurations

• Add one electron at a time according to these rules:

• 1. each added electron is placed in a sublevel of lowest energy available (Aufbau Process)

• 2. No more than 2 electrons can be placed in any orbital (Pauli Exclusion Principle)

• 3. Before a second electron can be placed in any orbital, all the orbitals of the sublevel must contain at least one electron (Hund’s Rule)

• 4. No more than 4 orbitals are occupied in the outermost principal energy level of any atom. (next electron must enter the next principal energy level)

NOW!!!!

• We will start writing electron configurations

•“Regular” and

• “Exceptions”

• Stanford explanation

Atoms absorb a SPECIFIC amount of Atoms absorb a SPECIFIC amount of energy – quantaenergy – quanta

Electrons “jump” up into energy Electrons “jump” up into energy levels where they really don’t belonglevels where they really don’t belong

Immediately drop back and release Immediately drop back and release that specific amount of energy in the that specific amount of energy in the form of light of specific wavelength form of light of specific wavelength and frequency (color)and frequency (color)

SpectroscopySpectroscopy

Used to study structure of atomsUsed to study structure of atoms substances heatedsubstances heated

– ee-- move to higher energy levels move to higher energy levels– ““fall back” - release photons of energy fall back” - release photons of energy

of specific wavelengthof specific wavelength produce a series of “spectral lines”produce a series of “spectral lines”

– are characteristic to specific are characteristic to specific substancessubstances

– used as an identifying toolused as an identifying tool

Ground state - Ground state - atom where the atom where the electrons are in the electrons are in the lowest available lowest available energy levelsenergy levels

excited state - excited state - atom has electrons atom has electrons that have that have “jumped” to higher “jumped” to higher energy levelsenergy levels

•Can identify elements by the colors they produce

•FIREWORKS!!!•Flame tests – lab we will do

• flame test lab!