II. Covalent Bonds

A. Three Types of Bonds Ionic Bonds Metallic Bonds Covalent Bonds Between a metal and nonmetal Electrons are transferred from the metal to the nonmetal Bond is attraction between positive cations and negative anions Metallic Bonds Between two metals Delocalized electrons attracted to positive metal ions Sea of Electrons (Electron Sea Model) Covalent Bonds Between two nonmetals Electrons are shared

B. Covalent Bond Properties Covalent bonds involve the sharing of a pair of valence electrons by two atoms

B. Covalent Bond Properties Cont. Covalent bonds form to create a noble gas configuration for each atom

C. Molecules A molecule is a neutral group of atoms joined together by covalent bonds. A diatomic molecule is a molecule consisting of two atoms

D. Diatomic Molecules 7 elements always exist in nature as diatomic molecules: Hydrogen (H2) Nitrogen (N2) Oxygen (O2) Fluorine (F2) Chlorine (Cl2) Iodine (I2) Bromine (Br2) Ways to remember: HONClBrIF NOF - 7

E. Properties of Molecules Molecules (covalently bonded compounds) tend to have relatively lower melting and boiling points than ionic compounds Sodium chloride (NaCl) melts at 801°C. Water (H2O) melts at 0°C and boils at 100° C.

F. Molecular Formulas A molecular formula shows how many atoms of each element a molecule contains. 2 hydrogen 1 oxygen 1 carbon 1 oxygen

REVIEW 1. Compared to ionic compounds, molecular compounds tend to have relatively low melting points and high boiling points. low melting points and low boiling points. high melting points and high boiling points. high melting points and low boiling points.

REVIEW 2. A molecule usually consists of two metal atoms and a nonmetal atom. two nonmetal atoms and a metal atom. two or more metal atoms. two or more nonmetal atoms.

REVIEW 3. A molecular formula shows how many atoms of each element a molecule contains. a molecule's structure. which atoms are bonded together. how atoms are arranged in space.

G. Naming Covalent Compounds 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa- 9 = nona- 10 = deca- Use prefixes to tell how many atoms of an element are present

G. Naming Covalent Compounds Cont. Rules: Name the elements in the order listed in the formula Use prefixes to indicate the number of each atom Do not use the prefix mono- when the first element in the formula contains only one atom Ex: CO2 = carbon dioxide not monocarbon dioxide Name of the second element ends in –ide

H. Covalent Compound Naming Exceptions Polyatomic Ions If the molecule has a charge it is a polyatomic ion. Use the names from the polyatomic ion list (quarter sheet). NO3– NO3 N3– SO32– SO3 S2– nitrate nitrogen trioxide nitride sulfite sulfur trioxide sulfide

Practice Name the following covalent compounds: NO2 CF4 H2O PI3 SF6

Practice carbon monoxide Pentacarbon decaoxide dinitrogen tetrasulfide xenon heptafluoride