Physical Chemistry

Chapters 1-5

The photoelectric effect

the process in which electromagnetic radiation ejects electrons from a material

All electromagnetic radiation is composed of

photons

All characteristics of the photoelectric effect are due to the interaction of individual photons

individual electrons

The maximum kinetic energy KE_e of ejected electrons (photoelectrons) is given by

KE_e = hv-Φ

The energy of light is proportional to its

frequency

increasing light intensity only increases the number of electrons released and not

their kinetic energy

define workfunction Φ

the minimum amount of energy necessary to remove an electron from the surface of a solid metal

Who discovered that white light was made up of colors of the rainbow?

Isaac Newton

what is the relationship between wavelength and frequency for electromagnetic radiation?

λv = c

define wavenumber

the reciprocal of wavelength that is directly proportional to energy

Ryderberg constant R_H

2.18E-18 J

What are Balmer lines?

a series of spectral lines from hydrogen, primarily in the visible spectrum, that result from an electron transitioning (falls) from a higher energy level (n>2) down to (n=2)

what does the de Broglie wavelength demonstrate in terms of “waves”?

there is a wave-particle duality of matter by connecting a particles momentum to its wavelength

what is the de Broglie’s wavelength equation

λ = h/p

As momentum increases what happens to the wavelength?

it decreases

particles and waves with short wavelengths correspond to what?

high energies

diffraction patterns are characteristics of what

wave-like behavior

diffraction occurs when waves encounter obstacles whose size is ________ with its wavelength

comparable

define interference in terms of waves

a phenomenon in which two or more waves superimpose to form a resultant wave of greater or lower amplitude and is the primary property used to identify wave behavior

do electrons have wave-like duality like photons?

yes

neutrons can act as waves but their contribution to the diffracted intensity is dependent upon what?

isotopes of the neutron because of how closely they interact with the nucleus of the atom

What is the Coulomb force?

a force that exists between oppositely charge particles

What is the Bohr model

quantized energy levels surrounding an atom explaining orbits as energy levels that electrons can jump from

what is the formula for Hooke’s Law?

F = -kx

what does Hooke’s Law state?

the force is proportional to, but in opposite direction to, the displacement (x)

what is the idea behind Hooke’s Law and diatomic molecule?

when atoms move away from their equilibrium positions, a restoring force is produced that increases proportionality with the displacement from equilibrium

what is Hooke’s law also referred to as?

the harmonic potential

define reduced mass

the representation of a two-body system as a single-body one

the zero-point energy is the __________ possible energy that a quantum mechanical physical system may have hence it is the energy of its ground state

lowest

in IR spectroscopy, transitions between vibrational energy levels can be induced about by __________ or __________ of radiation

absorption / emission

what are selection rules for IR transitions?

rules that limit which transitions will be observed or allowed

for IR absorption to occur, what 2 conditions must be met?

1. there must be a CHANGE in the dipole moment of the molecule

2. the frequency of the radiation matches the natural frequency of hte vibration