Overview
This lecture covers the structure of atoms, the periodic table, and explains the concepts of ions and isotopes, including how to calculate atomic composition.
Atoms and Elements
- Atoms are the basic units of matter, and elements are different types of atoms.
- The number of protons determines the element; each element has a unique number of protons.
- The periodic table uses symbols (e.g., C for carbon) as abbreviations for elements.
The Periodic Table and Atomic Numbers
- The atomic number (smallest number by the element symbol) shows the number of protons.
- The mass number (larger number) is the sum of protons and neutrons.
- Electrons do not significantly contribute to the atomic mass.
- Number of neutrons = mass number - atomic number.
Ions
- Atoms become ions by gaining or losing electrons, changing their overall charge.
- A neutral atom has equal protons and electrons.
- Positive ion: atom has lost one or more electrons.
- Negative ion: atom has gained one or more electrons.
- Protons and neutrons remain unchanged when ions form.
Isotopes
- Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
- Isotopes have the same atomic number but different mass numbers.
- Example: Hydrogen’s isotopes—protium (0 neutrons), deuterium (1 neutron), tritium (2 neutrons).
Key Terms & Definitions
- Atom — the smallest unit of an element, consisting of protons, neutrons, and electrons.
- Element — a substance made of atoms with the same number of protons.
- Atomic Number — number of protons in an atom.
- Mass Number — total number of protons and neutrons in an atom.
- Ion — an atom that has gained or lost electrons, resulting in a charge.
- Isotope — atoms of the same element with different numbers of neutrons.
Action Items / Next Steps
- Review atomic number, mass number, ions, and isotopes.
- (Optional) Watch the suggested video on the discovery and structure of atoms.