Lecture Notes: Nuclide Symbols

Introduction to Atoms

Atoms consist of:
- Protons: Positively charged particles in the nucleus.
- Neutrons: Neutral particles in the nucleus.
- Electrons: Negatively charged particles located outside the nucleus.
An element is defined by the number of protons in its nucleus.
- 1 proton = Hydrogen
- 2 protons = Helium
- 3 protons = Lithium
Atomic Number: Number of protons in the nucleus.
Mass Number: Total number of protons and neutrons in the nucleus.
- Protons and neutrons each have a mass of approximately 1 atomic mass unit.
- Electrons are negligible in mass calculations.

Represent elements using one or two-letter abbreviations.
- One letter: Capitalized.
- Two letters: First is capitalized, second is not.
Components of a nuclide symbol:
- Atomic Number: Sometimes shown at the bottom left.
- Mass Number: Shown at the top left, relevant for identifying isotopes.
- Charge: Indicated at the top right for ions.

Isotopes: Atoms of the same element with different numbers of neutrons.
- Mass number = protons + neutrons.
- Neutron count = Mass number - Atomic number.
Ions: Atoms with a net electrical charge due to differing numbers of electrons.
- Gain of electron(s): Atom has more electrons than protons (negative charge).
- Loss of electron(s): Atom has more protons than electrons (positive charge).

Arranged by increasing atomic number.
Atomic Mass: Averages of isotopic masses based on natural abundance.
- Not whole numbers due to averaging.
- Example: Chlorine has isotopes with mass numbers 35 and 37.
- Average mass reflects the relative abundance of isotopes.

Each element's position and atomic mass on the periodic table is determined by its protons, and isotopic abundance.
Individual atomic mass numbers are whole numbers.