Atomic And Nuclear physics Flashcards
Discovered that electrons could exist in certain specific states of definite energy without radiating away energy, if a certain condition was met by the orbit radius
Bohr
Geiger and Marsden’s alpha particles were largely deflected when the nucleus was approached at
Very short distances
Energy in electrons is thus… Because they lose energy when making a transition from one state to another of lower energy, and this emitted value equals the difference between states
Discrete
Under normal conditions, electrons occupy
Ground state
The set of wavelengths of emitted light by the atoms of an element is the
Emission spectrum
Electrons take energy and use it in order to make a transition. The wavelengths that are absorbed make the
Absorption spectrum
Number of protons in a nucleus is called the
Atomic number
Total number of nucleons in atom (protons+neutrons)
Mass number
Nuclei that have same atomic number but different mass number
Isotopes
Alpha, gamma, and beta radiations…. Air as they pass through it; knock electrons out of atoms
Ionise
Positive emissions; identical properties to helium nucleus. Mass number = 4 and atomic number = 2
Alpha
Negative emissions, identified as electrons.
Beta
Neutral emissions, identified as photons with small wavelengths
Gamma
Photons have wavelength of
hc/E
The number of nuclei that will decay per second is proportional to the number of atoms present that have not yet decayed.
Law of radioactive decay
Mass defect of the nucleus has been converted into …. And is stored in the nucleus
Binding energy
Binding energy equivalent to a mass of 1u
931.5 MeV
Produces neutrons, which can be used to collide with other nuclei producing a chain, self sustained reaction.
Fission when critical mass is present
….Creates… So that electrostatic repulsion between the two nuclei can be overcome
Fusion / plasma
Photoelectric effect; …. Of emitted light does not affect the energy of the emitted electrons
Intensity
Photoelectric effect; electron energy depends on… Of incident light and there is a certain minimum…. Below which no electrons are emitted
Frequency
Electrons are emitted with no time delay
Photoelectric effect
Energy of light quanta is given by
E=hf
If a photon of frequency f is absorbed by an electron, the electron’s energy will increase by
hf
The electron will be emitted only if
Hf>€
The difference between hf - €, will be the electron’s
Kinetic energy
When electron kinetic energy is zero
Hf=€
In photoelectric effect, electron’s kinetic energy equals
eVs
In a graph of stopping voltage vs frequency, one obtains a straight line with slope
h/e
Photon momentum given by
h / wavelength
Assigns wave like properties to particles
De broglie
To a particle of momentum p, there corresponds a wave of wavelength
h / p
Electron in a box model; electron confined within linear size L, h/p; cannot lose energy, wave is zero at the edges of the box and the wave will be related to L. It will be a
Standing wave
If a standing wave has wavelength 2L/n, what is its momentum?
nh/2L
What will the kinetic energy of an electron in the box model be?
(n^2*h^2)/(8mL^2)
Schrodingers theory assumes an associated wavefunction to… Of position and time
Electron
Can be used to find the probability that the electron will be found near x at t
|¥(x , t)|^2
When applied to hydrogen, Schrodingers theory predicts that an electron in the atom has quantised energy that depends on energy levels:
-13.6/n^2 , eV
Heisenberg states that it is not possible to measure simultaneously the position and momentum of something with indefinite precision
DxDp>=h/4pi
Nucleir radii depend on …. ; 1.2xA^(1/3)x10^-15
Mass number
Neutron decays into a proton, increasing atomic number by 1, an… And an…
Electron / antineutrino
A proton inside a nucleus may decay into a neutron, emitting a… And a…
Positron / neutrino
Since the energy of an electron in beta decay has a range of possible values, it means that….. To carry the remainder of available energy
A third light particle must be produced
Evidence that nucleus exists in discrete energy levels
Energies emitted from nuclear decay (i.e, alpha, gamma), are discrete
In radioactive decay, wavelength symbol represents
Decay constant; represents the probability of decay per unit time
