Overview
This lecture introduces chemical elements, their definition, basic properties, and significance in chemistry.
What Are Chemical Elements?
- Chemical elements are pure substances that cannot be broken down into simpler substances by chemical means.
- Each element is made up of only one kind of atom with a unique number of protons.
- There are about 90 naturally occurring elements, with more created artificially.
- Elements are the building blocks for all matter in the universe.
Atoms and Atomic Structure
- An atom is the smallest particle of an element that still retains its chemical properties.
- Atoms are composed of protons (positively charged), neutrons (neutral), and electrons (negatively charged).
- The atomic number, which equals the number of protons, identifies the element.
The Periodic Table
- The periodic table organizes all known elements by increasing atomic number.
- Elements in the same column (group) have similar chemical properties.
- Each element is represented by a unique chemical symbol (e.g., H for hydrogen, O for oxygen).
Uses and Importance of Elements
- All substances are made from elements, either alone or in combination as compounds.
- Living organisms rely on a small number of essential elements, such as carbon, hydrogen, and oxygen.
Key Terms & Definitions
- Chemical Element — A pure substance consisting of atoms with the same number of protons.
- Atom — The smallest unit of an element that retains its chemical identity.
- Atomic Number — Number of protons in an atom, unique to each element.
- Periodic Table — Structured chart organizing elements by atomic number and properties.
- Compound — Substance formed from two or more different elements chemically combined.
Action Items / Next Steps
- Review the periodic table and memorize the names, symbols, and atomic numbers of the first 20 elements.
- Read the corresponding section in your textbook for examples of everyday elements and their uses.