The Structure of matter Chapter 5

Section 1 compounds and molecules

Chemical bonds A chemical bond is the attractive force that holds atoms or ions together.

Chemical compounds Chemical compounds always have the same chemical formula. Chemical compounds are always made of the same elements in the same proportion.

Chemical structure The arrangement of atoms in a substance is known as its chemical structure. Bond length is the average distance between the nuclei of two bonded atoms.

Bond angle The bond angle is the angle formed by two bonds to the same atom.

Models of compounds Structural formulas Space-filling models

Section 2 ionic and covalent bonding

Ionic bonding An ionic bond is a bond formed by the attraction between oppositely charged ions. Electrons are transferred between atoms.

IONS Ions are atoms that have a charge. Metal atoms LOSE electrons and become positive. Positive ions are called CATIONS. Nonmetal atoms GAIN electrons and become negative. Negative ions are called ANIONS.

Properties of ionic compounds Usually involve the bonding between a metal and a nonmetal When melted or dissolved in water, they conduct electricity. Ionic compounds are in the form of networks not molecules.

Metallic Bonds A metallic bond is a bond formed by he attraction between positively charged metal ions and the electrons around them.

Covalent bonds A covalent bond is a bond formed when atoms share one or more pairs of electrons.

Electronegativity The ability of an atom to attract electrons to itself. 0-4 scale The difference in electronegativities between atoms determines the type of bond. Difference Type < 1.7 Covalent > 1.7 Ionic

Types of covalent bonds Nonpolar covalent Polar covalent Atoms share the pair of electrons equally Atoms do NOT share the electrons equally

Polyatomic ions A polyatomic ion is an ion made of two ore more atoms.

Section 3 compound names and formulas

Naming ionic compounds Name the cation. Name the anion with an –ide suffix. Special metals require us to determine their charge and then write the charge as a Roman numeral. Name polyatomic ions with no change to their suffix.

Naming covalent compounds Using a numerical prefix, name the first nonmetal. (Never use mono- on the first nonmetal) Using a numerical prefix, name the second nonmetal with an –ide suffix.

Types of formulas Empirical formula Molecular formula An empirical formula is a representation of the smallest whole number ratio of elements in a compound. The molecular formula is the actual ratio of elements in a molecule or unit of a compound.