 Polyatomic compounds combine polyatomic ions with metals  Poly atomic ions are groups of atoms that tend to stay together and carry an overall ionic charge e.g. Nitrate - NO 3 1-

Oxyacids: Compounds formed when hydrogen combines with polyatomic ions that contain oxygen

 Molecular compounds are groups of elements that come together and “share” electrons  When elements share electrons it is called a covalent bond  This is different from ionic bonding because it is the sharing of electrons that holds the compound together and not ionic charges

 In order to write formulas for molecular compounds you must know the combining capacity of the non-metals involved in forming a molecule  Combining capacity is a measure of the number of covalent bonds needed for a material to form a stable molecule (closed outer shell) How does it work? 1.Write the symbols, with their combining capacities above (always write the symbol with the highest combining capacity first) 42 CS 2.Use the crisscross method to determine each element’s subscript 42 CS C 2 S 4 CS 2 (reduced)

 Many molecular compounds have names similar to ionic compounds for example: H 2 S Hydrogen Sulfide  Others have common names; water (H 2 O), ammonia (NH 3 ), methane (CH 4 )  Molecular compound names often contain prefixes that refer to the amount of atoms of a given substance are present in each molecule: CO 2 Carbon dioxide CO Carbon monoxide

 Many nonmetallic elements exist as covalently bonded molecules.  These elements form Diatomic molecules (molecules made up of two similar atoms)