A. Three Types of Bonds • Ionic 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 • Use prefixes to tell how many atoms of an element are present • 1 = mono- • 2 = di- • 3 = tri- • 4 = tetra- • 5 = penta- • 6 = hexa- • 7 = hepta- • 8 = octa- • 9 = nona- • 10 = deca-
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– SO3S2– nitrate nitrogen trioxide nitride sulfite sulfide sulfur trioxide
Practice • Name the following covalent compounds: • NO2 • CF4 • H2O • PI3 • SF6
Practice • carbon monoxide • Pentacarbon decaoxide • dinitrogen tetrasulfide • xenon heptafluoride