9. Atomic and Nuclear Phenomena Flashcards
What is the photoelectric effect?
The photoelectric effect is the ejection of an electron from the surface of a metal in response to light
Electrons liberated from the metal by the photoelectric effect will produce a net charge flow per unit time, or current (I).
This supports the wave-particle duality.
Within the photoelectric effect, what is the threshold frequency?
The threshold frequency (ft) is the minimum light frequency necessary to eject an electron from a given metal
It’s dependent on the type of metal.
The threshold frequency is considered an ‘all or nothing’ response.
(Equation) What is the energy of a photon?
E=hf
- E= energy of the photon of light
- h= Planck’s constant (6.626 x 10-34 Joules x second)
- f= frequency of light/photon wave
If you know the frequency, you can easily find the wavelength by the equation c=fλ
What has a higher frequency:
Waves with shorter or longer wavelengths?
Which have a lower frequency energy?
High Frequency: short wavelength and higher energy
Low Frequency: longer wavelengths and lower energy
In regards to the photoelectric effect, how does the work function relate to the energy necessary to emit an electron from a metal?
The work function describes the minimum amount of energy necessary to emit an electron. Any additional energy from a photon will be converted to excess kinetic energy during the photoelectric effect.
In essence:
Original light energy= Kinetic energy + energy required to liberate electron
What does the threshold frequency depend on?
The threshold frequency depends on the chemical composition of a material (that is, the identity of the metal).
Kahn Academy: The threshold frequency is defined as the minimum frequency of incident radiation below which the photoelectric emission is not possible completely. irrespective of the intensity of incident radiation.
What electrical phenomenon results from the application of the photelectric effect?
The accumulation of moving electrons creates a current during the photoelectric effect.
What is fluorescence and what causes it to occur?
Fluorescence occurs when a species absorbs high-frequency light and then returns it to its ground state in multiple steps. Each step as less energy than the absorbed light and is within the visible range of the electromagnetic spectrum.
The wide range of colors in fluorescent lights, from the whitish green of office lighting to the glaring colors of neon signs is the result of the distinct multistep emission spectra of different fluorescent materials.
What determines 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, such as protonation and deprotonation, change in oxidation state or bond order, and others may cause dramatic changes in light absorption in a material.
During which electronic transitions is photon emission most common?
When electrons transition from a higher-energy state to a lower-energy state, they will experience photon emission.
What is the nuclear binding energy?
Nuclear binding energy is the amount of energy that is released when nucleons (protons and neutrons) bind together.
The more binding energy per nucleon released, the more stable the nucleus.
What is the mass defect when discussing nuclear binding energy?
Laymans terms: When protons and neutrons come together to form a nucleus, you would expect their individual masses to equal the mass of the nucleus. But they do not. This is called the mass defect. The lost mass is lost in energy, related by the equation
E=mc2
The mass defect is the difference between the mass of the unbonded nucleons and the mass of the bonded nucleons within the nucleus.
When you have protons and neutrons that form a nucleus, why doesn’t it break apart? After all, the protons have positive charges and repel each other?
When protons and neutrons come together to form the nucleus, they are attracted to each other by the strong nuclear force, which is strong enough to more than compensate for the repulsive electromagnetic force between the protons.
How do you define the following?
Strong nuclear force
Mass defect
Binding energy
Strong Nuclear Force: The strong nuclear force is one of the four primary forces and provides the adhesive force between the nucleons (protons and neutrons) within the nucleus.
Mass Defect: Mass defect is the apparent loss of mass when nucleons come together, as some of the mass is converted into energy.
Binding Energy: the mass that is converted into energy when nucleons come together
What is isotopic notation? What do the following mean?
X= element
Z= protons
A= neutrons
What is the definition of fusion?
Fusion occurs when small nuclei combine into larger nuclei
Example- the sun powers itself by fusing four hydrogen nuclei to make one helium nuclus. This produces 3.85 x 1026 joules per second
Energy is released in both fusion and fission because the nuclei formed in both processes are more stable than the starting nuclei.
What is the definition of fission?
Fission occurs when a large nucleus splits into smaller nuclei.
Spontaneous fission rarely occurs
Example: power plants.
Energy is released in both fusion and fission because the nuclei formed in both processes are more stable than the starting nuclei.
What is alpha decay? How do we denote it?
Alpha decay is the release of a helium (aka alpha) atom. It contains:
- two protons
- two electrons
- 0 electrons
The emission of an alpha particle means that the atomic number of the daughter nucleus will be two less than that of the parent nucleus, and the mass number will be four less.
What is beta negative decay? How do we denote it?
Beta-negative decay is the decay of a neutron into a proton, with emission of an electron and an antineutrino.
What is beta positive decay? How do we denote it?
Beta-positive Decay, also called positron emission, is the decay of a proton into a neutron, with emission of a positron (e+ and B+) and a neutrino (v)
What is gamma decay and how do we denote it?
Gamma decay (γ) is the emission of a gamma ray, which converts a high energy nucleus into a more stable nucleus.
A gamma ray is a high energy photon
They carry no charge and just lower the energy of the parent nucleus without changing the mass number or the atomic number
What is electron capture and how do we denote it?
Electron capture is the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron.
