Forming Compounds

Ionic compounds Most elements like to “hang out” to make them stable They give up or gain electrons to form compounds so they are less reactive. Ionic compounds Always contain a metal and non-metal The metal atom gives it’s valence electron to the non metal atom But…how are they held (bonded) together?? Metal Non-Metal CATION(positive charge) ANION(negative charge)

The cation and the anion are attracted to each other (this attractions is called an ionic bond Ionic Bonds are very strong and result in the following properties: Soluble in water High melting/boiling points Conduct electricity when dissolved in water Hard and brittle Lattice structure

Naming Ionic Compounds: The name of the metal always comes first, then the non-metal Change the ending of the non-metal to “ide” Writing Formulas for Ionic Compounds: Write the symbol for each element. Add the charge that each element forms Criss-cross the number in the charge Don’t write any 1s in the formula Reduce the subscripts to lowest terms

Example: Write the formula for calcium iodide Answer: CaI2 (see below)

Covalent Compounds Formed between 2 non-metals. The non-metals share electrons with each other, making each atom “feel” like it has a full shell of its own. This sharing of electrons results in a covalent bond. Example: chlorine gas

Naming Covalent Compounds: Because 2 non-metal elements can combine to form more than one stable compound we must use a naming system that distinguishes between them Step 1 – name the elements in the same order as in the formula Step 2 – name the second element but change the ending to “ide” Step 3 – start both words with a prefix to indicate how many of each atom is present in the compound

Examples: NO _______________________ N2O _______________________ NO2 _______________________ N2O3 _______________________ N2O4 __________________________________ N2O5 _______________________ CO2 _______________________ P2O5 _______________________ CH4 _______________________ NH3 _______________________