What are the main components of an atom?
Nucleus (protons and neutrons) and orbiting electrons.
What does the atomic number (Z) represent?
The number of protons in the nucleus; determines the element.
What does the mass number (A) represent?
The total number of protons and neutrons in the nucleus.
What is an atomic mass unit (amu)?
1/12 the mass of a carbon-12 atom; ~1.66 × 10⁻²⁷ kg.
What is the relative mass and charge of a proton?
Mass = 1 amu; charge = +1e.
What is the relative mass and charge of a neutron?
Mass = 1 amu; charge = 0 (neutral).
What is the relative mass and charge of an electron?
Mass ~1/1836 amu; charge = –1e.
What are electron shells?
Regions around the nucleus where electrons reside, labeled K, L, M, etc.
What rule gives the maximum number of electrons per shell?
2n² rule, where n = shell number (K=1, L=2, etc.).
How many electrons can the K shell hold?
2 electrons (2 × 1²).
How many electrons can the L shell hold?
8 electrons (2 × 2²).
How many electrons can the M shell hold?
18 electrons (2 × 3²).
What is binding energy of an electron?
The energy required to remove an electron from its shell, expressed in eV or keV.
What is the relationship between binding energy and distance from nucleus?
Binding energy decreases with increasing distance from nucleus (outer shells have lower binding energy).
How does atomic number (Z) affect binding energy?
Higher Z → higher binding energy for all shells.
What is the K-edge?
The sudden increase in x-ray attenuation when photon energy exceeds the K-shell binding energy.
What is the strong nuclear force?
A fundamental force that binds protons and neutrons together in the nucleus.
What is the electrostatic (Coulomb) force in atoms?
The repulsive force between protons and the attractive force between protons and electrons.
What determines nuclear stability?
The balance between strong nuclear force and electrostatic repulsion among protons.
What is the Segré chart?
A plot showing stable and unstable isotopes based on proton-neutron ratios.
What are isotopes?
Atoms with the same number of protons (same Z) but different numbers of neutrons (different A).
What are isobars?
Nuclei with the same mass number (A) but different atomic numbers (Z).
What are isotones?
Nuclei with the same number of neutrons but different Z.
What is a nuclide?
A species of atom defined by its number of protons and neutrons.
