Nuclear Physics - The Atom and Its Components

Matter: All matter is comprised of atoms.
Atoms: The smallest unit into which a chemical element can be divided without losing its chemical identity.
Molecules: Formed when atoms combine together.
Examples of Elements:
- Oxygen (O)
- Hydrogen (H)
- Water (H₂O)

Atoms are made up of subatomic particles including protons, neutrons, and electrons.
Nucleus: The atomic nucleus is made of protons and neutrons, which are collectively known as nucleons.
Protons: Positively charged particles found in the nucleus.
Neutrons: Neutral particles with a mass slightly greater than that of a proton, also found in the nucleus.
Electrons: Negatively charged particles that orbit the nucleus and are considered to have negligible mass.

Proposed by Niels Bohr in 1913.
- Protons: +1 charge, mass approximately 1,836 times that of an electron.
- Neutrons: 0 charge, mass slightly greater than a proton.
- Electrons: -1 charge, zero mass; exist in definite energy levels or orbits around the nucleus.

Particle	Charge	Mass (amu)	Mass/Energy (MeV)	Location in Atom
Proton	+1	1.007276	938.272	Nucleus
Neutron	0	1.008665	939.565	Nucleus
Electron	-1	0.000549	0.511	Extranuclear

Atoms are mainly composed of empty space, with over 99.9% of the mass located in the nucleus.
The nuclear force refers to the force that holds nucleons together in the nucleus.

Neutrons are unstable outside of the nucleus and will convert into a proton and an electron in approximately 17 minutes.
Neutrons are stable within the nucleus unless they undergo radioactive decay.

In a stable atom, the number of electrons equals the number of protons.
Electrons reside in stable orbits or shells within the atom where they can exist indefinitely without losing energy.

The diameters of the electron shells are determined by quantum numbers (n):
- K-shell: n = 1
- L-shell: n = 2
- M-shell: n = 3
- N-shell: n = 4
The maximum number of electrons that can occupy each shell is given by the formula: $2n^2$ .

Electrons can transition between orbitals; energy is released as a photon when an electron moves from a higher to a lower energy level.
The naming of orbitals corresponds to energy levels, with farther orbitals from the nucleus having higher energy.

Example for Technetium (Tc): Electron Shells: 2, 8, 18, 13, 2
General configuration representation:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰

Electrons are held in atoms by electrical forces, with greater binding energies observed in higher atomic number elements.
The closer the electron is to the nucleus, the stronger the binding energy.
- Higher binding energy indicates it requires more energy to remove an electron.

Negative Binding Energy: Indicates energy needed to liberate the electron from the atom.

Nuclide: Any distinct arrangement of protons and neutrons in the nucleus with a measurable lifetime.
Isotopes: Nuclides with identical atomic numbers (Z) but differing mass numbers (A).
Isotones: Nuclides with the same neutron number but differing mass numbers.
Isobars: Nuclides with the same mass number but differing atomic numbers.
Isomers: Nuclides that share the same mass number and atomic number, but have different energy states of the nucleus.

Isotope Examples: Different isotopes of iodine include I-125, I-127, I-131, where Z remains constant but A varies, affecting physical properties.
Example of Isotopes of Hydrogen:
- Hydrogen-1 (protium): 1p+ 0n
- Hydrogen-2 (deuterium): 1p+ 1n
- Hydrogen-3 (tritium): 1p+ 2n

Line of Stability: Graphical representation of stable vs. radioactive nuclides plotted by neutron number (n) against proton number (p).
Primary Decay Modes: Includes various decay processes such as alpha decay, beta decay, and electron capture.

A chart representing various isotopes alongside their neutron and proton counts, labeling stability and decay type.