Chemical Formulas and Chemical Compounds

Chapter Seven

Unit Three

Review the Periodic Table

Horizontal rows – periods

Vertical rows – groups or families

Metals – left of stairstep and at the bottom

Non-metals – right of stairstep

Metalloids – 6 elements touching stairstep

Characteristics of Metals Shiny (have luster) (most are solids) Silvery or gray colored (except gold and copper) Conduct electricity (gold is best along w/Ag, Cu,

and Al) Ductile – can be pulled into a wire Malleable – hammered into a thin sheet (Au most,

then Ag and Cu) Always lose e- from their outer energy level to form

positive ions called cations Place charges at top of groups (+1 +/-4) – this is

the # of e- in the outer energy level that can be lost

Characteristics of Non-metals

No luster, powdery, liquid or gaseous (not solids) Colored rather than silvery Nonconductors of electricity Not ductile Not malleable Always gain e- into their outer energy level until

they have 8; form negative ions called anions Place charges at top of groups (+/-4 -1); this is

the # of e- needed to be gained to reach 8

Oxidation Numbers Also called oxidation states Indicate general distribution of e-

among bonded atoms Useful in naming compounds, writing

formulas, and balancing equations These #s are most often = to ionic

charge

Chemical Names and Formulas

Chemical formulas form the basis of the language of chemistry.

They reveal information about the substance.

Binary Ionic Compounds Binary – two different elements Ionic – metal with a non-metal # of negative and positive charges

must be equal (no net charge) Cation (metal) is always written first (+

charge) Ionic charge is never included

Binary Molecular Compounds

Binary – 2 elements Molecular – compounds of only non-metals One of the non-metals assumes a +

oxidation # and is written first More electronegative element remains

negative These compounds are named differently

because there is no metal present

Acid-a distinct type of molecular

compound; most are binary or oxyacids

Binary Acids-acids that consist of 2 elements, usually

hydrogen and one of the halogens (F, Cl,

Br, I)

Oxyacids-acids that contain

H, O, and a 3rd element, usually a nonmetal (HNO3)

Ionic Salts Ionic compound composed of a cation and

the anion from an acid (NaCl, Na2SO4, LiNO3)

Some salts contain anions in which one or more H atoms from the acid are retained; such anions are named by adding the word hydrogen or the prefix bi- to the anion name Ex: (H2SO4 HSO4

-) sulfuric acid to hydrogen sulfate or bisulfate ion

Hydrates Written as a correct ionic formula

followed by a dot and then some number of molecules of water (CuSO4 5H20)

You need to be able to recognize these and know how to name them.

Empirical Formula consists of the symbols for the elements

combined in a compound, with subscripts showing the smallest whole-# mole ratio of the different atoms in the compound

for ionic compounds, formula unit is usually compound’s empirical formula

for molecular compounds, empirical formula doesn’t necessarily indicate actual #s of atoms present in the molecule