Chapter 2 Flashcards
Photoelectric effect
Metals emit electrons when light shines upon them
Electromagnetic spectrum
Low energy, low frequency, long wavelength
High energy, high frequency, short wavelength
quantum-mechanical model
a model that explains the strange behavior of electrons
wave–particle duality of light
Certain properties of light are best described by thinking of it as a wave, while other properties are best described by thinking of it as a particle
electromagnetic radiation
a type of energy embodied in oscillating electric and magnetic fields.
Electromagnetic radiation speed in vacume
3 x 10^8 m/s
We can characterize a wave by?
amplitude and its wavelength
amplitude
the vertical height of a crest
wavelength (λ)
the distance between adjacent crests (or any two analogous points) and is measured in units such as meters, micrometers, or nanometers.
color
Determined by the wavelength
frequency (ν)
the number of cycles (or wave crests) that pass through a stationary point in a given period of time.
electromagnetic spectrum
Visible light makes up only a tiny portion of it
interference
Waves, including electromagnetic waves, interact with each other in a characteristic way
constructive interference.
if two waves of equal amplitude are in phase when they interact—that is, they align with overlapping crests—a wave with twice the amplitude results.
destructive interference.
two waves are completely out of phase when they interact—that is, they align so that the crest from one overlaps with the trough from the other
diffraction
When a wave encounters an obstacle or a slit that is comparable in size to its wavelength, it bends (or diffracts) around it and results in an interference pattern
binding energy
the energy with which the electron is bound to the metal.
Relationship between energy and frequence
E = hv (where v is frequence)
Photon
A packet of light
KE of ejected photon
KE = hv - B.E (B.E is binding energy)
emission spectrum
The range of wavelengths emitted by a particular element
Niels Bohr
develop a model for the atom that explained atomic spectra. In his model, electrons travel around the nucleus in circular orbits (analogous to those of the planets around the sun). Bohr’s orbits exist only at specific, fixed distances from the nucleus. The energy of each Bohr orbit is also fixed, or quantized. Bohr called these orbits stationary states
Electron transition
The energy of the photon emitted when an electron makes a transition from one stationary state to another is the energy difference between the two stationary states. Transitions between stationary states that are closer together, therefore, produce light of lower energy (longer wavelength) than transitions between stationary states that are farther apart.
absorption spectrum
dark lines on a bright background
electron interference
the interference pattern is not caused by pairs of electrons interfering with each other, but rather by single electrons interfering with themselves.
de Broglie relation
The wavelength (λ) of an electron of mass m moving at velocity v
The Uncertainty Principle
we cannot simultaneously measure its position and its velocity with infinite precision.
complementary properties
Complementary properties exclude one another—the more we know about one, the less we know about the other.
Heisenberg’s uncertainty principle
the product of Δx and mΔv must be greater than or equal to a finite number (h/4π).
indeterminacy
Unlike a baseball, whose future path is determined by its position and velocity when it leaves the pitcher’s hand, the future path of an electron is indeterminate and can only be described statistically.
an orbital
a probability distribution map showing where the electron is likely to be found
ψ is the wave function
a mathematical function that describes the wavelike nature of the electron. A plot of the wave function squared represents an orbital, a probability density distribution map of the electron.
principal quantum number
n
angular momentum quantum number
l
magnetic quantum number
m sub l
spin quantum number
m sub s (1/2 or -1/2)
energy of an electron in an orbital with quantum number n
E = -2.18 * 10^-18 [1/n square final - 1/n square initial]
Electron spin
The spin quantum number specifies the orientation of the spin of the electron.
principal level (or principal shell)
Electrons with the same value of n
sublevel
Orbitals with the same value of n and l
probability density
a three-dimensional plot of the wave function squared
A node
a point where the wave function (ψ), and therefore the probability density and radial distribution function, all go through zero.
