Chapter – 6 Oct 24, 2011 Part - BChapter – 6 Oct 24, 2011 Part - B

The legends of physical sciencesThe legends of physical sciences

The De Broglie’s Equation

In 1924 Louis De Broglie proposed that

electrons do not behave like solid

particles, but they behave like waves.

Louis De Broglie(1892 – 1987)

De Broglie suggested that the wavelength

of a particle of mass m moving at speed v

is,

h = plank’s constantmvh

This relation provides the link between the

description of electron as a particle and as a wave

The Schrodinger’s Wave Equation

developed this idea and solved

wave equations to make predictions

about where an electron may be

found in an atom.

Edwin Schrodinger(1887 – 1961)

Schrodinger’s wave equations , when solved, identifies a region in space around the nucleus where there is a 90% probability of finding an electron with a specified energy.  

The Heisenberg Uncertainty Principle

When you try to observe the wave nature of the

electron, you cannot observe its particle nature

and vice versa, we cannot locate electrons and

simultaneously observe their wave nature.

it is impossible to simultaneously measure the position and momemtum of an electron with exactitude.

Werner Heisenberg 1901-1976

Indeterminacy of Electrons

A baseball follows a well-defined

trajectory from the hand of the

pitcher to the mitt of the catcher.

The catcher can see the trajectory

of the ball and predict correctly to

place the mitt in the right place to

catch the ball.

However, electrons do not follow

a fixed path to predict, we can only

have a statistical map when

electrons can be found under a

given set of conditions.

Probability Distribution Map

If the baseball displayed wave-particle duality, the path of the baseball

could not be precisely determined.

The best we could do would be to make a probability distribution map

of where a "pitched" electron will cross home plate.

In the quantum-mechanical model, specific electron orbits are not

appropriate: the electron's movement cannot be known that precisely.

Instead, we map the probability of finding the electron at various

locations outside the nucleus.

The probability map is called an orbital.