Chemistry Ch. 6 - Electronic Structure of Atoms

Quantum Theory

Describes an atom’s arrangement/electronic structure and behavior

1. Number of electrons

2. Distribution about the nucleus

3. Energy of electrons

Quantum Mechanics

Describes atoms correctly

Electronic Structure

Number of electrons, distribution, and charge in the nucleus

What causes atoms to glow/emit light

Because of energy changes

Electromagnetic Radiation aka Radiant Energy

Light energy that is in waves

1. Electric field

2. Magnetic field

and travels at the speed of light, c = 3 × 10⁸ m/s

Wavelength (λ)

Is the length between each peak/dip, measured in meters or nanometers

Frequency (v)

The number of complete waves per second, measure in 1/s or s^-1 or Hertz (Hz)

What is the Electromagnetic Radiation Spectrum Order

Wavelength and frequency are inversely proportionate. Just know the order and relationships, but not the numbers.

Common Wavelength Units in Electromagnetic Radiation

Speed of Light

c = 3 × 10⁸ or c = λv (frequency x wavelength), frequency and wavelength are inversely proportional

Behavior of Light

1. Blackbody radiation - Emits a light when heated (a stove coil turning red)

2. Photoelectric Effect - Emits electrons from metal surfaces when light shines

3. Emission Spectra - Emits electrons

Blackbody radiation

Light is emitted when heated, wavelength depends on the temperature, not the surface or composition
Ex) A stove glowing red

Max Planck (1900)

Energy can be released/absorbed only in packets of quantum and E=hv

1. Energy exists at small levels

2. A single quantum energy is, E= constant(h) x frequency(v), h = 6.626 × 10^-34
   Ex) For each temperature, there is a maximum intensity for the radiation

Threshold Frequency

The minimum energy required to emit electrons from metal, 1.602 × 10^-19

1. A lower threshold ejects no electrons

2. A higher threshold ejects electrons with radiation and kinetic energy

Binding Energy

Energy needed to remove an electron

Photon

A stream of tiny energy packets

Rydberg equation

Used to calculate the wavelengths for hydrogen.
Use the smaller one for n1, and the larger number for n2
R_H=1.097 × 10⁷m^-1

Limitations of the Bohr Model

1. It cannot predict the shape of multi-electron atoms

2. Electrons have wave properties and do not circle in perfect circles

3. We cannot know their exact location

4. Electrons exist in specific energy levels

5. Energy is involved when moving energy levels

Representation of Orbitals

1. S - spherical shape, holds 2 electrons, 1 orientation (m_l=0), l=0

2. P - dumbbell shape, holds 6 electrons, 3 orientations (m_l= -1, 0, 1), l=1

3. D - four leave clover shape, holds holds 10 electrons, 5 orientations (m_l= -2, -1, 0, 1, 2), l=2

4. F - ring shape, holds 14 electrons, 7 orientations (m_l= -3,-2,-1, 0,+1,+2,+3), l=3