Download Arrangement of Electrons in Atoms

Chapter 4
ARRANGEMENT OF ELECTRONS IN ATOMS
THE DEVELOPMENT OF A NEW ATOMIC MODEL

Light has characteristics of both particles and waves

Electromagnetic radiation – a form of energy that
exhibits wave-like behavior as it moves through space

Electromagnetic spectrum
ELECTROMAGNETIC SPECTRUM

 = wavelength (units of meters)

 = frequency (units of Hertz, Hz,

c = speed of light (3.00 x 108 m/s)
h = Planck’s constant (6.626 x 10-34 Js)


1
seconds
1

c  
E  h
)
EMISSION AND ABSORPTION

Ground state – the lowest energy state of an atom

Excited state – when an atom has a higher
potential energy than it does at its ground state

Balmer series – represents
visible light region

Lyman series – represents the
UV region

Paschen series – represents
the infrared series
EMISSION LINE SPECTRA

When a narrow beam of light is passes through a prism,
it separates into specific colors in the visible spectrum.
Each element has a signature spectrum.
EMISSION SPECTRA

In addition to indicators in the visible spectrum,
energy can be detected in the UV region as well as
the infrared region. This has been scientifically
observed.
What wavelengths represent indicators in the UV range? What about the IR range?
EMISSION SPECTRA
Scientists had predicted that emission spectra
would be on a continuous spectrum.
Is this what was scientifically observed?
BOHR’S MODEL AND TRANSITION STATES

Bohr’s Model helped to explain the quantum energy levels of
the atom

When a photon is absorbed, the electron gains enough
energy to move to an outer energy level.

When an electron loses energy (in the form of a photon),
energy is released.
ELECTRON ENERGY TRANSITIONS
PHOTOELECTRIC EFFECT

Recap – what is the relationship between
energy and frequency of a wave?

What is the visible region of light? Which colors
in the visible spectrum carry more energy?

http://www.youtube.com/watch?v=0qKrOFgJZ4
HOMEWORK

P.97, #1-6 (2 days to complete)
QUANTUM MODEL OF THE ATOM

Electrons have wavelike properties

Investigations from
the photoelectric
effect and
hydrogen’s emission
line spectra
determined that light
acts as both a wave
and a particle.
ELECTRONS

Electrons have interference patterns
Constructive interference
Destructive interference
DOUBLE SLIT EXPERIMENT

http://www.youtube.com/watch?v=DfPeprQ7o
Gc
HEISENBERG



Heisenberg’s Uncertainty Principle – you
cannot know the instantaneous position and
velocity of an electron (or any other particle)
x – represents position
p – represents momentum
(velocity multiplied by mass)
 - represents a constant
Δ – in this case, delta
represents the uncertainty.
When you have extremely precise information
about x, your uncertainty for p goes through the
roof.
ORBITALS

Orbitals indicate probable electron locations

Schrodinger’s equation!
This formed the foundation of modern quantum theory

Quantum theory –

Quantum numbers –
PRINCIPLE QUANTUM NUMBER

Symbolized by n

Indicates the main energy level occupied by an
electron.
 True

or false – these can only be integers
The total number of orbitals in a given shell is
equal to n2!
ANGULAR MOMENTUM QUANTUM NUMBER

Different orbital shapes can exist for each
principle quantum number.

Represented by l
 What
orbital shapes could you find at n=3?
 What about when n=3 and l=2?
MAGNETIC QUANTUM NUMBER

Represented by “m”
 Ranges

from –l to l
Indicates the orientation of an orbital around
the nucleus
SPIN QUANTUM NUMBER

Represented by “s”

Has only two possible states

A single orbital can hold a maximum of two
different electrons
SMARTBOARD DEMONSTRATION
LET’S PRACTICE! CLASS WORK

How many electrons could be represented by n=2?

How many electrons could be represented with a
principle quantum number of 3 and an angular
momentum quantum number of 0?

How many electrons could be represented with a
principle quantum number of 1 and a spin number of ½?

How many electrons could be represented with a
principle quantum number of 3 and a spin number of ½?

How many electrons could be represented by l=3?