Quantum Physics and Atomic Structure Practice Flashcards

These flashcards cover the core concepts of atomic structure, specific charge, the photoelectric effect, energy levels, line spectra, and wave-particle duality as presented in the Quantum Physics lecture notes.

According to the Rutherford-Bohr model of the atom, which particles compose the nucleus and which particles are in orbits?

Protons and neutrons compose the nucleus, while electrons are in orbits or shells centered on the nucleus.

In the notation $\phantom{}_Z^A X$, what do $A$ and $Z$ represent?

$A$ is the nucleon number (total number of nucleons), and $Z$ is the proton number (the number of protons).

What is the approximate scale difference between the diameter of an atom and the diameter of its nucleus?

The nucleus is about $100,000$ times smaller than the atom; the diameter of an atom is approximately $10^{-10}\,m$, while the nucleus is approximately $10^{-15}\,m$.

How do positive and negative ions differ in their electron-to-proton ratio?

Positive ions have fewer electrons than protons, whereas negative ions have more electrons than protons.

What is the definition of isotopes?

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.

For calculations in Physics Paper 1, what is the standard value used for the mass of a proton or neutron?

$$1.67 \times 10^{-27}\,kg$$

How is specific charge defined and what are its SI units?

Specific charge is the charge per unit mass for a particle, nucleus, or ion, measured in $C\,kg^{-1}$.

What is the value of one electronvolt (eV) in Joules (J)?

$$1\,eV = 1.60 \times 10^{-19}\,J$$

Define the threshold frequency ($f_0$) in the context of the photoelectric effect.

The minimum frequency of light required to emit electrons from the surface of a metal.

What is the work function ($\phi$) of a metal?

The minimum energy needed to remove an electron from the surface of a metal.

State Einstein’s photoelectric equation relating photon energy, work function, and kinetic energy.

$hf = \phi + E_k(\text{max})$, where $E_k(\text{max})$ is the maximum kinetic energy of the photoelectrons.

How is the energy of a photon related to its frequency ($f$) and wavelength ($\lambda$)?

$E = hf = \frac{hc}{\lambda}$, where $h$ is Planck's constant ($6.63 \times 10^{-34}\,Js$) and $c$ is the speed of light ($3 \times 10^8\,m/s$).

What is stopping potential ($V_s$)?

The potential difference required to reduce the photoelectric current to zero because the maximum kinetic energy has been reduced to zero ($eV_s = E_k(\text{max})$).

What experimental evidence suggests that particles like electrons possess wave properties?

Electron diffraction.

What experimental evidence suggests that electromagnetic waves have a particulate nature?

The photoelectric effect.

State the de Broglie wavelength equation for a particle with momentum ($mv$).

$$\text{de Broglie wavelength} = \frac{h}{mv}$$

Define excitation and de-excitation in an atom.

Excitation is where an atomic electron gains an exact amount of energy to move to a higher energy level; de-excitation is where it loses the energy difference by emitting a photon to move to a lower level.

Define ionization energy.

The minimum energy required to remove an electron in the ground state from an atom.

How does a fluorescent tube produce visible white light?

Mercury vapor is excited by electron collisions and emits UV photons; these are absorbed by a phosphor coating, which then de-excites in a cascade to emit visible light of multiple wavelengths.

Why are the energy levels in an atom denoted as negative values?

A free electron is defined as having an energy of $0$ at the infinity level ($\infty$), so bound electrons within the atom have less energy than a free electron.