The Structure of Matter Chapter Five

When two or more elements react, a compound is formed When two or more elements react, a compound is formed. The compound will have different properties from the elements that make it up.

The forces that hold elements together in a compound are called chemical bonds.

Compounds are different from mixtures because they: Have a definite chemical formula. Cannot be separated by physical means.

Chemical bonds give molecules a chemical structure Chemical bonds give molecules a chemical structure. Chemical structure is determined by bond angle and bond length.

Chemical Structure can be shown by: Structural formulas: O H H Space Filling Models:

The elements of some compounds form strong, network bonded solids.

The molecules of some compounds are bound into networks bonded liquids and some might not be bonded at all and exist as gases.

Molecules are often held together by hydrogen bonds.

Ionic and Covalent Bonding Section Two

When valence electrons interact, chemical bonds form, and atoms give off energy to make a more stable compound.

Chemical bonds are flexible as electrons are interchanged and the nuclei move back and forth.

Ionic bonds are formed when electrons are transferred leaving oppositely charged ions to attract each other.

Obviously, ionic compounds do not have single molecules Obviously, ionic compounds do not have single molecules. Thus, the formula for an ionic compound actually represents a formula unit. Not all ionic compounds react in a one to one ratio.

Ionic compounds: Form between a metal and a nonmetal. Conduct electricity when melted or dissolved. Form geometric crystals.

In covalent bonds, two or more nonmetals share electrons to gain a stable octet.

Covalent bonds form between two nonmetals and: (1)are independent molecules (2) usually form liquids and gases. (3) don’t conduct electricity

Sometimes the sharing arrangement is not even and forms a polar covalent bond.

Sometimes groups of atoms share electrons but have to lose or gain electrons. This forms polyatomic ions.

Writing and Naming Compounds Section

Metal atoms react with other metal atoms to form metallic bonds.