Ch. 3 – Compounds

3.1 Compounds are pure substances made of more than one kind of atom joined together are held together with chemical bonds. two basic types: covalent and ionic. See pages 76 - 78

Covalent compounds share electrons to form molecules Example: water

Ionic compounds atoms gain or lose electrons to form ions Example: NaCl

The positive ions attract all of the negative ions, and vice versa. In ionic solids, the ions are packed together into a repeating pattern called a crystal lattice. The positive ions attract all of the negative ions, and vice versa. Example: Table salt (NaCl) has a one-to-one ratio of ions which creates a simple square-shaped ionic crystal: See page 78

Polyatomic Ions (PAIs) Covalent & ionic bonds can occur together A polyatomic ion is created when a covalently bonded molecule gains or loses electrons becoming charged Example: Hydroxide ion (OH-) See pages 79 - 80

There are many types of PAIs, but they occur in a few basic shapes. Take the Section 3.1 Quiz