Overview
This lecture introduces chemical bonding, focusing on distinguishing between ionic and covalent compounds, their formation, and key properties.
Metals, Non-metals, and Metalloids
- Elements are classified as metals, non-metals, or metalloids on the periodic table.
- Metals are colored red, metalloids yellow, and non-metals blue on the referenced periodic table.
- Examples: Lithium (metal), Neon (non-metal), Boron (metalloid).
- Metals are generally good conductors; non-metals are poor conductors; metalloids have intermediate properties.
Introduction to Compounds
- Compounds consist of two or more elements chemically bound together.
- Table salt (sodium chloride, NaCl) is an example of a compound.
Chemical Bonding
- Chemical bonding is the lasting attraction between atoms, ions, or molecules to form compounds.
- Atoms bond to become stable.
Ionic Bonding
- Ionic bonding occurs through the complete transfer of electrons from one atom to another.
- Usually forms between metal and non-metal elements.
- Results in ions: atoms or molecules with a positive or negative charge.
- Metals lose electrons to form cations (positive ions); non-metals gain electrons to form anions (negative ions).
- Example: Sodium (metal) transfers an electron to Chlorine (non-metal) to form NaCl.
Covalent Bonding
- Covalent bonding involves the sharing of electron pairs between atoms.
- Commonly occurs between two non-metals.
- Non-metals have high electronegativity and share electrons for stability.
- Example: Two hydrogen atoms share electrons with one oxygen to form H₂O (water).
- Types:
- Non-polar covalent: electrons are shared equally (e.g., H₂).
- Polar covalent: electrons are shared unequally due to differences in electronegativity (e.g., H-F).
Properties of Ionic vs. Covalent Compounds
- Ionic compounds: solid state, high melting/boiling points, very hard/brittle, low conductivity, soluble in water, not malleable or ductile, low volatility.
- Covalent compounds: can be solid, liquid, or gas; lower melting/boiling points; not very hard; very low conductivity; insoluble in water, soluble in organic solvents; higher volatility; not malleable or ductile.
Key Terms & Definitions
- Compound — Substance formed by two or more elements chemically bound together.
- Chemical bonding — Attraction that enables atoms, ions, or molecules to form compounds.
- Ionic bond — Bond formed by complete transfer of electrons from a metal to a non-metal.
- Covalent bond — Bond formed by sharing electron pairs between non-metals.
- Ion — Atom or molecule with a positive (cation) or negative (anion) charge.
- Valence electron — Electron in the outermost shell of an atom.
Action Items / Next Steps
- Review the periodic table to practice identifying metals, non-metals, and metalloids.
- Memorize properties of ionic and covalent compounds for comparison.
- Understand examples of each type of bonding for possible quiz questions.