Wave Particle Duality &Electron Configurations

Remember Rutherford? Proposed model of the atom had a nucleus of

positive charge surrounded by a relatively large area of empty space where electrons orbited

Did not propose an arrangement for the electrons

Did not explain why the electrons were not pulled into the nucleus (attraction of opposite charges)

Light as a Wave Light exhibits characteristics of waves

Wavelength (λ)

Frequency (ν)

amplitude

Electromagnetic Waves Different types

Each type has characteristic λ and ν

All parts travel with the speed of light (c)… 3.00 x 108 m/s

Electromagnetic Wave Formula

𝑐= λν

EXAMPLE PROBLEM 5.1 Microwaves are used to cook food and

transmit information. What is the wavelength of a microwave that has a frequency of 3.44 x 109 Hz?

Now You Try:Practice Problems 1 – 4 on page 140

The Particle Nature of Light Objects that are heated often give off a

characteristic color (red of stove burner, white of light bulb)

View of light as a wave did not provide an accurate explanation of why this occurs

So….

Max Planck (1858 – 1947) Concluded that energy could only be

gained or lost in small, specific amounts (like tiny packages)…called these amounts quanta

Energy of a Quantum

E = hν

The Photoelectric Effect Another phenomenon that could not be

explained with light as a wave

When light of a certain minimum frequency shines on a metal’s surface, the metal will eject electrons (video)

Example 5.2 Every object gets its color by reflecting a

certain portion of incident light. The color is determined by the wavelength of the reflected photons, thus by their energy. What is the energy of a photon from the violet portion of the Sun’s light if it has a frequency of 7.230 x 1014 s-1?

Atomic Emission Spectra Also called line spectra…not continuous

Set of frequencies of electromagnetic waves emitted by an element

Not continuous

Unique for each element (like a fingerprint)

Electron Configurations Bohr

› Model stated that atoms orbit the nucleus in definite paths (energy levels)

› Patterned this model after planets orbiting the sun

› Electrons in a particular path (energy level) have a fixed amount of energy…quantized

› Energy levels are analogous to the rungs on a ladder

Bohr’s Model Based on a hydrogen atom

Assigned a quantum number (n) to each orbit

As value of n increases, the amount of energy increases

Energy relationships…

∆𝐸=𝐸 (h h𝑖𝑔 𝑒𝑟 𝑜𝑟𝑏𝑖𝑡 )−𝐸 (𝑙𝑜𝑤𝑒𝑟 𝑜𝑟𝑏𝑖𝑡 )=𝐸 ( h𝑝 𝑜𝑡𝑜𝑛 )=h𝑣

Limitations of Bohr’s Model Worked well for hydrogen

Did not explain the atomic spectra produced by any other elements

The Quantum Mechanical Model of the Atom

Louis de Broglie (1892 – 1987) › Recognized that electrons exhibited

characteristics of waves› Recognized that light has properties of

both waves and particles› Theorized that matter must be able to

possess qualities of waves and particles as well

de Broglie Equation: Predicts that all matter has wave

characteristics

Heisenberg Uncertainty Principle

States that it is fundamentally impossible to know both the precise velocity (momentum) and location of a particle at the same time

Applies to all matter, but is useful only with really small particles…like electrons

Electron Configurations Schrodinger

› Revised Bohr’s model› Mathematical equation to determine the

most likely place an electron would orbit the nucleus

› Gives the probability of finding an electron in a particular place within the atom

Quantum Numbers Used to describe orbitals Specify the properties of atomic

orbitals and the properties of the electrons in the orbitals

4 Quantum Numbers First three derived from the

Schrodinger equation:› Main energy level (n)› Shape of orbital (l)› Orientation of orbital (ml)

Fourth is the spin quantum number (ms)› Describes the fundamental state of the

electron

Principal Quantum number Symbolized by n Indicates the main energy level occupied

by an electron Values are positive integers As n increases, so does the distance from

the nucleus More than one electron can have the same

n Total number of orbitals for a given energy

level is given by n2

Angular Momentum Quantum Number

Each main energy level (except the 1st) has different orbitals of different shapes

Symbolized by l Indicates the shape of the orbital The number of orbital shapes possible

for each energy level is equal to the value of n

The values of l allowed are zero through n-1

Angular Momentum Quantum Number

Depending on the value of l, the orbital is assigned a letter

0=s 1=p 2=d 3=f

Shapes of sub-orbitals s = spherical p = dumbbell shaped d= complex f = way to complicated to explain…see

illustrations

Atomic orbitals are designated by the n followed by the letter of the sublevel

Magnetic Quantum Number Orbitals can have the same shape, but

different orientations around the nucleus

Magnetic quantum numbers indicate the orientation (ml)

s orbitals have only one orientation p orbitals can extend along the x, y, or

z axis 3 p sublevels (px, py, or pz)

Magnetic Quantum Numbers

Values for m sublevels correspond values m = -1 m=0 and m=1

5 different d orbitals…therefore 5 different orientations

m=-2 m=-1 m=0 m=+1 m=+2 7 different f orbitals….7 orientations

Spin Quantum Numbers Electrons spin on an internal axis Can spin in one of two possible

directions Spin quantum numbers can be +1/2 or

-1/2 A single orbital can hold a maximum of

2 electrons The electrons in a single orbital must

have opposite spins

Electron Configurations Remember:

› All electrons can be described by a set of quantum numbers

› No two electrons can have the same set of quantum numbers

Rules for Electron Configurations

Aufbau Principle› An electron will occupy the lowest energy

orbital that can receive it Pauli Exclusion Principle:

› No 2 electrons in the same atom can have the same set of quantum numbers

Hund’s Rule:› Orbitals of equal energy are each occupied by

one electron before any orbital is occupied by a second electron….All electrons in singly occupied orbitals have the same direction of spin (parallel spin)

Energy Level Types of Orbitals

1 s

2 s, p

3 s, p, d

4 s, p, d, f

5 s, p, d, f

6 s, p

7 s, p

Orbital Type # Sub-orbitals

s 1

p 3

d 5

f 7

Sub-orbitals Each sub-orbital can hold two electrons

The electrons in a sub-orbital must have opposite spin

Type of Orbital Max # electrons

s 2

p 6

d 10

f 14

Energy Level Types of Orbital Max # of e-

1 s 2

2 s, p 8

3 s, p, d 18

4 s, p, d, f 32

5 s, p, d, f 32

6 s, p, 8

7 s, p 8

Electron Configurations & the Periodic Table

s, p, d, f blocks

s - block

1 s2 s3s4 s5s6 s7 s

p - block

5p

2p3p4p

6p7p

d - block

5d

3d4d

6d

f - block

4f5f

Give the Electron Configurations:

Carbon

Lithium

Sodium

Phosphorus

Neon

You Try: Write the complete electron configuration

for:› Helium

› Sulfur

› Magnesium

› Silicon

› Tin

Show orbital notations for: Carbon

Lithium

Sodium

Phosphorus

Neon

You try Write the orbital notation for:

› Helium

› Sulfur

› Magnesium

› Silicon

› Tin

Noble Gas Notations Use the noble gas that comes before

the element

Write the noble gas’s symbol in brackets

Continue with the electron configuration from there

Noble Gas Notation Example Calcium:

› Electron Configuration:

› Noble Gas Notation:

You try these:a. Titaniumb. Siliconc. Barium