The Quantum Model of the Atom

Chapter 4 Section 2

Proposed that the photoelectric effect

could be explained by the concept of

quanta, or packets of energy that only

occur in specific amounts.

Einstein expanded this concept to

propose that all electromagnetic

radiation has this dual wave-particle

nature. He proposed the photon, a

mass-less particle that carries a quantum

of energy.

Max Planck

Emission Spectra

Elements will emit light

of certain frequencies as

their electrons return

from the excited state to

the ground state.

Each has a unique

pattern that makes it

identifiable (like a

fingerprint).

His model of the Hydrogen atom

sought to explain how the gas

could emit only certain

frequencies, and thus colors, of

light.

It was successful in explaining H,

but failed to do so with multi-

electron atoms.

Niels Bohr

In 1924 he proposed that

electrons, like light, may

demonstrate wave-particle

duality.

Experiments like the

double-slit experiment opened

the door to verification of

quantum ideas.

Louis de Broglie

Developed the wave equations

that describe mathematically the

wave properties of electrons and

other small particles. These

equations define the probable

locations of electrons, or

orbitals.

Erwin SchrÖdinger

Developed the Uncertainty

Principle which states that is

impossible to determine

simultaneously both the position

and velocity of a particle. The

act of observing changes the

event!

Let’s let some prominent

physicists explain.

Werner Heisenberg

Say my name?

Heisenberg Humor

I’m not the

Heisenberg we’re talking

about…II

Atomic Orbitals

Atomic orbitals and

the electrons in

them can be

described by a set

of four quantum

numbers.

1.Principal Quantum Number (n) tells how many energy levels (or shells) are occupied by electrons. Values from 1-7. Increase values indicate higher energy and further distance from the nucleus.

2.Angular Momentum Quantum Number (l) indicates the shape of the orbital. There are 4 main shapes designated s, p, d and f.

3.Magnetic Quantum Number (m) indicates the orientation of the orbital around the nucleus along the x, y and z axis’.

4.Spin Quantum Number indicates the possible spin state of the electron. Values are +1/2 and -1/2.

Quantum Numbers

Basic orbital shapes

S = Spherical

P = Peanut

D = Double peanut

F = Flower

Mnemonic for Orbital Shapes