Chemistry - Modern Atomic Theory

Principle Quantum Number

The principle quantum number, symbolized by n, indicates the main energy level occupied by the electron

Ex: n=1, n=2, n=3…

Aufbau Principle

Electrons must enter orbitals of low energy first

Pauli Exclusion Principle

An orbital can hold only two electrons at a time, the electrons will have opposite spins.

Hund’s Rule

Electrons fill orbitals one at a time (w/ the same spin until they are forced to pair up).

Valence Electron

Electron in the highest energy level

Quantized

Electron is limited to certain positions in the atom

Only certain values are allowed

Heisenberg’s Principle of Uncertainty

You cannot simultaneously define the position and momentum (m*v) of an electron

Orbital

The region of space within which an electron is found - area of probability - not exact location

E. Schrodinger

Developed the wave equation, wave function

Quantum Mechanics Theoretical; Schrodinger’s Cat

Something can be dead or alive w/ a closed box, until you open the box, it HAS to be one or the other

Types of Orbitals

S-Orbital - sphere

P-Orbital - dumbell

D-Orbital - 3 waves

S-Orbital

As you go from one energy level to the next, the wave gets bigger

P-Orbital

The three p orbitals lie 90 degrees apart in space

Niels Bohr

Built a simple model of the atom

Based on an understanding of the sharp line emissons spectrum

Line Emissions Spectra

When atoms or molecules absorb energy, that energy is often released as light energy.

When that light is passed through a prism, a pattern is seen that is unique to that type of atom or molecule - the pattern is called an emissions spectrum

• non-continuous

Line emission Spectra of Excited Atoms

Excited atoms emit light of only certain wavelengths

The wavelengths of emitted light depend on the element

Problems with Bohr’s Atomic Line Spectra

Theory was only successful for H

Introduced quantum idea artificially

Energy of Photon

Energy of a photon is directly proportional to its frequency

Frequency of Light

Frequency of light is inversely proportional to it’s wavelength