Chapter 9 Flashcards
photoelectric effect
the ejection of electrons from a metal when light (of high enough frequency) hits it
threshold frequency
the minimum frequency of light that causes ejection of electrons
(Depends on the type of metal being exposed to the radiation)
photon
a particle representing a quantum of light; composes a light beam
energy of a photon equation
E = hf
E → photon energy
h → Planck’s constant
f → frequency of light
frequency of light equation
c = f λ
c → speed of light
f → frequency
λ → wavelength
if the frequency of a photon is at the threshold frequency for the metal…
the electron will just barely escape (with no extra energy)
if the frequency of a photon is above the threshold frequency for the metal…
the excess energy will be converted to kinetic energy in the ejected electron
maximum kinetic energy of the ejected electron equation
Kmax = hf – W
h = Planck’s constant f = frequency of light W = work function of the metal in question
Work function (definition and equation)
the minimum energy required to eject an electron
W = hfT
h = Planck’s constant
fT = frequency threshold
Atomic absorption
An electron can jump from a lower energy to a higher energy orbit if it absorbs a photon with the same energy as the difference between orbits
Atomic emission
how does fluorescence work?
the UV radiation excited the molecules to a higher energy state, and then when they return to ground state, they emit photons
nucleons
protons and neutrons
Mass defect
the apparent loss of mass when protons and neutrons come together and some of the mass is converted to energy
the difference between the mass of the unbonded nucleons and the bonded nucleons within the nucleus
Binding energy
the energy released when the nucleons come together
isotopic notation
Fusion
small nuclei combine to form a larger nucleus
Fission
radioactive decay
a naturally occurring spontaneous decay of certain nuclei accompanied by the emission of specific particles
alpha particle
a helium nucleus (2 protons and 2 neutrons
atomic mass = 4
atomic number = 2
alpha decay
an unstable nucleus changes to another element by shooting out an alpha particle
positron
β- decay
a neutron is converted into a proton and a β- particle (electron) is emitted
β+ decay (positron emission)
a proton is converted to a neutron and a β+ particle (positron) is emitted
gamma ray
high-energy (high frequency) photons
no charge
Lower the energy of the parent nucleus without changing the mass number or the atomic number
Gamma decay
the emission of a gamma ray; the high energy nucleus is converted into a more stable nucleus
electron capture
half life
the amount of time required for half of a sample of radioactive nuclei to decay
