Chapter 7 sections 3 and 4

1. Chapter 7 sections 3 and 4

2. Section 3: Formulas for Ionic Compounds • Formula Unit represents the simplest ratio of ions involved in a chemical compound • NaCl= one sodium ion and one chloride ion • Monatomic ions are one atom ions that can be either a cation or an anion • Mg+2 or Cl- • Oxidation number is the charge of the monatomic ion and equals the number of valence electrons transferred to or from an atom • O-2 has an oxidation number of -2

3. Formulas for binary ionic compounds • Always write the cation first • Ca+2 comes before O-2 = CaO • The anion is always last in the formula • O-2 comes after Ca+2 = CaO • Practice Problems on page 221 • Potassium and iodide • Magnesium and chloride • Aluminum and bromide • Cesium and nitride

4. Formulas for polyatomic ionic compounds • Polyatomic ions are ions that contain more than one type of element • The charge of a polyatomic ion applies to the entire group, NOT just one atom or element in the group • The rules for writing formulas are the same as binary compounds • Higher oxidation number is written first • Lower oxidation number is written last

5. Formulas for polyatomic ionic compounds (cont.) • NEVER change the subscripts of the atoms in the polyatomic ion • Simply place the polyatomic ion in parentheses and then add the subscript • (NH4)2O • Practice problems page 222 • Sodium and nitrate • Calcium and chlorate • Aluminum and carbonate

6. Names for Ions and Ionic Compounds • Oxyanionis a polyatomic ion consisting of an element bonded with oxygen • When more than one oxygen atom is present, it requires special rules for naming • For Sulfur(S) and Nitrogen(N) follow these rules: • The ion with the greatest number of oxygen atoms end in the suffix –ate. • The ion with fewer oxygen atoms ends in the suffix -ite.

7. Rules for Halogens The greatest number of oxygen atoms is prefixed with per- and suffixed with –ate. One fewer oxygen atom ends with the suffix –ate. 2 fewer oxygen atoms end with the suffix –ite. 3 fewer oxygen atoms is prefixed with hypo- and suffixed with –ite.

8. Practice Problems page 223 NaBr CaCl2 KOH Cu(NO3)2 Ag2CrO4

9. Recap of Rules for naming Ionic Compounds • Name the cation followed by the anion • For monatomic cations use the element name • For monatomic anions use the root of the element name and end in –ide • For elements with multiple oxidation numbers, write the oxidation number in parentheses after the element name. E.G. Fe+2 + O-2 = FeOcalled Iron(II) Oxide • When a polyatomic anion is present, name the cation first, then follow with the polyatomic anion. Example: NaOH is sodium hydroxide • When a polyatomic cation is present, name the polyatomic cation first, then follow with the anion Example: (NH4)2S

10. Section 7.3 Assessment Complete numbers 34-39 Homework if not finished in class!

11. Section 4: Metallic Bonds and the Properties of Metals Metallic bonds are similar to ionic bonds in that the bonds are based on attraction of unlike particles- positive and negative Both metals and ionic compounds form a lattice structure when solid

12. Metallic Bonds Electron sea model says that all metal atoms contribute valence electrons in a metallic solid, i.e. they share their electrons Delocalized electrons are the electrons that are moving freely in a metallic solid Metallic bonds form when a metallic cation is attracted to delocalized electrons

13. Properties of Metals • Melting and boiling points are moderately high for most metals • Boiling points are extremely high for most metals because it takes a lot of energy to remove the metallic cation from the electron sea • Malleability, ductility, and durability are all due to the electron sea configuration of the atoms • It is extremely difficult to remove the metallic cations from the delocalized electrons so they slide past each other rather than break off.

14. Properties of Metals (cont.) • Thermal and electrical conductivity are very high due to the delocalized electrons. • They are free to move between metallic cations in the solid. • Hardness and strength increase as the number of delocalized electrons increase • The number of electrons each atoms has to contribute determines the number of delocalized electrons

15. Metal Alloys • An alloy is a mixture of elements that has metallic properties. • The properties of alloys vary depending on the composition of the alloy or the manufacturing process used to make the alloy • Steel consists of iron and another element and it is stronger than iron alone • Steel can also be made stronger by heating and cooling it during the manufacturing process

16. Metal Alloys (cont.) • Substitutional alloys are alloys made when atoms of the original element are replaced by atoms of another element with a similar atomic size • The alloy gains the properties of both elements • Interstitial alloys are alloys made when small holes in the crystal lattice get filled in with smaller atoms • For example: carbon steel is iron and carbon. This combination makes the alloy harder, stronger, and less ductile than iron.

17. Section 7.4 Assessment Page 228 numbers 40-45 Homework if not finished in class LAB TOMORROW!