Atomic and Nuclear Phenomena Flashcards
What is the photoelectric effect?
The photoelectric effect is when a source of light with a high enough frequency (blue or ultraviolet light) is shined onto a metal sheet cauing the emission of electrons from the sheet of metal.
- The ejection of electrons from the sheet of metal produces a current (flow of charge per unit of time).
What is the Threshold Frequency (fT)?
The Threshold Frequency is the minimum frequency of light required to eject an electron from a material.
- The Threshold frequency depends on the type of metal being exposed to the radiation (the chemical composition of the material).
What are the two equations used to calculate the energy of each photon proportional to the frequency of light?
E = hf or E = (hc/wavelength)
- Frequency (f) = speed of light (c) / wavelength
What is the work function (W)?
The work function (W) is the minimum energy required to eject an electron. It’s formula is:
W = h x fT
- h = Plank’s constant
- fT = Threshold Frequency
How does the work function relate to the energy necessary to emit an electron from a metal?
The work function (W) describes the minimum amount of energy required to emit an electron.
- Any excess energy will be converted into excess kinetic energy during the photoelectric effect.
What does the threshold frequency depend upon?
The threshold frequency (fT) depends upon the chemical composition of a material (that is, the identity of the metal).
- The Threshold frequency (fT) is the minimum frequency of light required to eject an electron from a material.
What electrical phenomon results from the application of the photoelcetric effect?
The accumulation of moving electrons produced during the photoelectric effect creates a current (flow of charge per unit of time).
How is Infrared (IR) spectroscopy and UV - VIS spectroscopy used to determine the chemical composition of a molecule?
IR and UV - VIS spectroscopy are used to determine chemical structure because different bonds will absorb different wavelengths of light. Different bonds correspond to specific wavelengths.
What deteremines the absorption spectrum of a single atom?
The energy differences between ground-state electrons and higher-level electron orbits determine the frequencies of light a particular material absorbs (its absorption spectrum).
True or False?
Small changes in chemical structure only minimally impact light absorption and emission patterns.
False
Small changes in chemical structure (such as protonation/deprotonation, oxidation state, bond order, and others) may cause dramatic changes in the light absorption in a material.
During which electronic transitions is photon emission most common?
When electrons are absorbed (transition from higher to lower energy state/orbit) they will experience photon emission.
What is fluorescence and what causes it?
Fluorescence is a special stepwise photon emission in which an excited electron returns to the ground state through on or more intermediate excited states. Each energy transition releases a photon of light. With smaller energy transitions thant the initial energy aborbed (causing electron to become excited), these fluorescent materials can release photons of light within the visible range.
What is the Strong Nuclear Force?
The strong nuclear forces is the adhesive force that holds the nucleus together.
What is the Mass Defect?
The mass defect is the apparent loss of mass when nucleons come together to from a nucleus. This is why the actual mass of a nucleus for every atom (except hydrogen) is lower than the sum of all the protons and neutrons within the nucleus of an atom.
- The mass is converted into energy
What is binding energy?
Binding energy is the energy that is created from the conversion of mass to energy during the binding of nucleons to form a nucleus.
- Binding energy can calculated using the equation E = mc2
- m = mass (difference of mass between atomic mass and the actual mass = mass defect)
