AP Chemistry Unit 3

Wavelength formula

c = wavelength x frequency

Speed of light

c = 3 × 10⁸ m/s

Quantum Theory and Planck

Energy increases in full, discrete units called quantums

Energy per quantum

E = hv (planck’s constant x frequency)

Planck’s constant

6.63 × 10^-34

Photoelectric effect

Low frequency light does not eject electrons. Once it hits the threshold frequency, electrons are ejected immediately. Increasing the intensity of the light increases the electron ejection rate. Increasing the frequency increases the velocity of the electrons

Wavelength of visible light

ROY G. BIV, smallest to greatest

Atom absorbing a photon

An electron moves up one energy level. The energy change is equal to the energy of the photon and difference between energy levels

Atom emitting photons

An electron moves down one level. The energy change is equivalent to the energy of the photon or the difference in energy levels

Hybrid Orbital Theory

Atomic orbitals in the same atom combine to form hybrid orbitals, atomic orbitals of different atoms overlap to form covalent bonds

Spectroscopy formula

Intensity of electromagnetic radiation entering the object = intensity of electromagnetic radiation emitted by the object + intensity of electromagnetic radiation absorbed by the object

What is UV/Vis spectroscopy used for?

Examines transitions in energy levels, probes for the electronic structure of certain compounds, determines concentrations of solutions that contain certain compounds

What are the peaks in the UV/Vis spectroscopy graphs?

Energy level transitions

What wavelength of UV light can colorless species absorb in UV/Vis spectroscopy

200nm-400nm

Beer’s Law

A = Ebc (Absorbance = molar absorbance x path length x concentration)

What is IR spectroscopy used for

Determine changes in molecular vibrations to detect the different types of bonds present and the identity of the molecule

What is microwave spectroscopy?

Microwaves causes polar molecules to rotate, they have specific rotational frequencies, can be used to determine diatomic bond length and shape