Chapter 6 Chemical Names and Formulas Charles Page High School Dr. Stephen L. Cotton

Section 6.1 Introduction to Chemical Bonding OBJECTIVES: Distinguish between ionic and molecular compounds.

Section 6.1 Introduction to Chemical Bonding OBJECTIVES: Define cation and anion, and relate them to metal and nonmetal.

Molecules and Molecular Compounds About 100 different elements Millions of compounds from them Naming is essential in chemistry Noble gases, such as He and Ne Isolated atoms- monatomic, they consist of single atoms

Molecules and Molecular Compounds Molecule- smallest electrically neutral unit, still has properties of the substance Made from only nonmetals Can be from one element- O2 Can make a compound- CO2

Molecules and Molecular Compounds Properties of molecular compounds Low melting and boiling points Usually gas or liquid Composed of two or more nonmetals O2, O3, H2O

Systematic Naming There are too many compounds to remember the names of them all. Compound is made of two or more elements. Put together atoms. Name should tell us how many and what type of atoms.

Atoms and ions Atoms are electrically neutral. Same number of protons and electrons. Ions are atoms, or groups of atoms, with a charge (positive or negative) Different numbers of protons and electrons. Only electrons can move. Gain or lose electrons.

F1- O2- Anion A negative ion. Has gained electrons. Nonmetals can gain electrons. Charge is written as a superscript on the right. Has gained one electron (-ide is new ending= fluoride) F1- O2- Gained two electrons (oxide)

K1+ Ca2+ Cations Positive ions. Formed by losing electrons. More protons than electrons. Metals can lose electrons K1+ Has lost one electron (no name change for positive ions) Ca2+ Has lost two electrons

Ionic Compounds Ionic compounds- from joining metal cations and nonmetal anions- they are electrically neutral Usually solid crystals Melt at high temperatures

Two Types of Compounds Molecular compounds Made of molecules. Made by joining nonmetal atoms together into molecules.

Two Types of Compounds Ionic Compounds Made of cations and anions. Metals and nonmetals. The electrons lost by the cation are gained by the anion. The cation and anions surround each other. Smallest piece is a FORMULA UNIT.

Two Types of Compounds Ionic Molecular Smallest piece Formula Unit Molecule Types of elements Metal and Nonmetal Nonmetals Solid, liquid or gas State solid Melting Point High >300ºC Low <300ºC

Section 6.2 Representing Chemical Compounds OBJECTIVES: Distinguish among chemical formulas, molecular formulas, and formula units.

Section 6.2 Representing Chemical Compounds OBJECTIVES: Use experimental data to show that a compound obeys the law of definite proportions.

Chemical Formulas Shows the kind and number of atoms in the smallest piece of a substance. Molecular formula- number and kinds of atoms in a molecule. CO2 C6H12O6

Chemical Formulas More than one atom? –use a subscript (H2O) There are 7 diatomic elements Hydrogen (H2), Nitrogen (N2), Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2) Remember: “Br I N Cl H O F”

Ionic Compounds This formula represents not a molecule, but a formula unit The smallest whole number ratio of atoms in an ionic compound. Ions surround each other so you can’t say which is hooked to which. (p. 140)

Some Laws: 1. Law of Definite Proportions- in a sample of a chemical compound, the masses of the elements are always in the same proportions. H2O (water) and H2O2 (hydrogen peroxide)

Some Laws: 2. Law of Multiple Proportions- Dalton stated that whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers. Figure 6.11, p. 141

Section 6.3 Ionic Charges OBJECTIVES: Use the periodic table to determine the charge on an ion.

Section 6.3 Ionic Charges OBJECTIVES: Define a polyatomic ion, and give the names and formulas of the most common polyatomic ions.

Charges on ions For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location; monatomic ions Elements in the same group have similar properties. Including the charge when they are ions.

1+ 2+ 3+ 3- 2- 1-