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Chapter 3. Elements Combine to Form Compounds. Chapter 3. 3.1 Compounds. Chemical Reaction. What are the indicators that a chemical reaction has occurred? Potassium Chlorate and a Gummy Bear. Ion Charge Revisited.
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Chapter 3 Elements Combine to Form Compounds
Chapter 3 3.1 Compounds
Chemical Reaction What are the indicators that a chemical reaction has occurred? Potassium Chlorate and a Gummy Bear
Ion Charge Revisited What determines the ion charge or combining capacity for a particular element? • The ion charge is determined by the number of valence e- in the outer shell that an element wants to donate or borrow. Example: Ca = +2 Na = +1 Cl = -1
Metals vs. Nonmetals From the periodic table, can you locate metals and nonmetals? What type of ions do metals form? • Metals have positive (+) charges. • They want to donate an e- (or electrons)from their outer shell. What type of ions do nonmetals form? • Most non-metals have negative (–) charges. • They want to accept an e- (or electrons)into their outer shell.
Compounds What is a compound? • Compounds are pure substances made of more than one type of element • Most compounds are one of 2 basic types: • Covalent • Ionic
Covalent Compounds • Atoms combine by sharing valence electrons Example. Water Hydrogen gas What would Carbon dioxide look like? • Covalent bonding usually occurs between 2 non-metals • Example: C and O share electrons to form CO (carbon monoxide) – try to draw it!
Covalent vs. Ionic Bonding http://www.youtube.com/watch?v=QqjcCvzWwww http://www.youtube.com/watch?v=xTx_DWboEVs&NR=1
Ionic Compounds • Atoms gain or lose electrons and form ions. • The charges of the ions are attracted to the opposite charge; therefore a compound is produced. • Example. Na+ and Cl- combine to form NaCl (salt) NOTE: • In covalentcompounds, atoms combine by sharing electrons to form molecules.
Ionic Bonds • Lead to the formation of crystal lattices. • All the ions are attracted to all other ions in the crystal, although nearest ions have the greatest attraction. • Repeating pattern of negative and positive charges. • Think in terms of ratios. • NaCl is a ratio of one sodium to one chlorine, but many NaCl molecules will form a crystal lattice.