Chapter 8.5 Polarity

Polarity is the separation of electric charge that leads to a bond or molecule having a positive and negative end –An unequal pull or sharing of electrons –Based upon electronegativity –An atoms tendency to attract electrons –Indicate polarity with a δ + and δ - –Three main types of bonds (dealing with polarity) Polarity

Nonpolar Bond –Also known as a Pure Covalent Bond –A bond between two atoms that have very similar electronegativity (less than 0.4 difference) –Usually identical atoms (same element) –The pull of electrons is the same/symmetrical –Example: Polarity

Polar Bond –Also know as a Polar Covalent Bond –A bond between two atoms that have different electronegativity values (0.4 to 2.0 difference) –The pull of electrons is not equal/asymmetrical –Most bonds are polar –Example Polarity Notice the dipoles (δ + and δ - ) which indicate where unequal sharing of electrons is taking place in the molecules.

Ionic Bond –A bond between two atoms that have very different electronegativity values (greater than 2.0 difference) –Always between a metal and nonmetal –The pull of the more electronegative atom (nonmetal) is strong enough to pull the electron from the less electronegative atom (metal) Polarity

Polar and Nonpolar Molecules –A molecule can be made up of polar bonds, but is nonpolar overall –Take a look at the shape (3D) and determine if the unshared electrons are symmetrical or asymmetrical Polarity

Polar and Nonpolar Molecules Polarity

Naming Molecular Compounds Chapter 8.2

Naming Molecular Compounds Type III –two nonmetals but no polyatomic ions –Name the elements as you see them in the formula –The last element has –ide for an ending –Each element has a prefix referring to the number of ATOMS (not electrons) 1 = mono6 = hexa 2 = di7 = hepta 3 = tri8 = octa 4 = tetra9 = nona 5 = penta10 = deca

Naming Molecular Compounds Type III –If the first element is mono, drop it from the name (all other monos are kept) –Monocarbon monoxide  Carbon monoxide –When “ao” or “oo” are created when combining a prefix with element name, drop the first vowel –Monooxide  Monoxide –Decaoxide  Decoxide –Trioxide  Trioxide

Naming Molecular Compounds Examples –CCl 4 –Carbon tetrachloride –P2O3–P2O3 –Diphosporus trioxide –IF 7 –Iodine heptafluoride

Naming Molecular Compounds Now try going from the name to the chemical formula –Dinitrogen trioxide –N2O3–N2O3 –Dichlorine octoxide –Cl 2 O 8 –Carbon tetrabromide –CBr 4 –Dihydrogen monoxide –H2O–H2O