Chemical Formulas and Chemical Compounds

1. Chemical Formulas and Chemical Compounds Chapter Seven Unit Three

2. 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

3. 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

4. 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

5. 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

6. Chemical Names and Formulas • Chemical formulas form the basis of the language of chemistry. • They reveal information about the substance.

7. 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

8. 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

9. Acid -a distinct type of molecular compound; most are binary or oxyacids Binary Acids Oxyacids -acids that consist of 2 elements, usually hydrogen and one of the halogens (F, Cl, Br, I) -acids that contain H, O, and a 3rd element, usually a nonmetal (HNO3)

10. 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

11. 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.

12. 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