The ELECTRON: Wave  Particle Duality

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The ELECTRON: Wave – Particle Duality. Graphic: www.lab-initio.com. The Dilemma of the Atom. Electrons outside the nucleus are attracted to the protons in the nucleus Charged particles moving in curved paths lose energy What keeps the atom from collapsing?. Wave-Particle Duality.

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### The ELECTRON: Wave – Particle Duality

Graphic: www.lab-initio.com

The Dilemma of the Atom
• Electrons outside the nucleus are attracted to the protons in the nucleus
• Charged particles moving in curved paths lose energy
• What keeps the atom from collapsing?
Wave-Particle Duality

JJ Thomson won the Nobel prize for describing the electron as a particle.

His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron.

The electron is a particle!

The electron is an energy wave!

The Wave-like Electron

The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.

Louis deBroglie

Electromagnetic radiation propagates through space as a wave moving at the speed of light.

c = 

c = speed of light, a constant (3.00 x 108 m/s)

 = frequency, in units of hertz (hz, sec-1)

 = wavelength, in meters

The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation.

E = h

E= Energy, in units of Joules (kg·m2/s2)

h= Planck’s constant (6.626 x 10-34 J·s)

= frequency, in units of hertz (hz, sec-1)

Long

Wavelength

=

Low Frequency

=

Low ENERGY

Wavelength Table

Short

Wavelength

=

High Frequency

=

High ENERGY

Answering the Dilemma of the Atom
• Treat electrons as waves
• As the electron moves toward the nucleus, the wavelength shortens
• Shorter wavelength = higher energy
• Higher energy = greater distance from the nucleus

This produces bands

of light with definite wavelengths.

Spectroscopic analysis of the hydrogen spectrum…

…produces a “bright line” spectrum

Flame Tests

Many elements give off characteristic light which can be used to help identify them.

strontium

sodium

lithium

potassium

copper

Exclusion Notice

The contents of the next two slides reference equations that are no longer included on the AP Chemistry equations sheet, and can no longer be tested in a quantitative sense

Electron Energy in Hydrogen

Z= nuclear charge (atomic number)

n= energy level

***Equation works only for atoms or ions with 1 electron (H, He+, Li2+, etc).

Calculating Energy Change, E, for Electron Transitions

Energy must be absorbed from a photon (+E) to move an electron away from the nucleus

Energy (a photon) must be given off (-E) when an electron moves toward the nucleus