The Structure of Matter

1. The Structure of Matter Section 1 – Compounds and Molecules Section 2 – Ionic and Covalent Bonding Section 3 – Compound Names and Formulas

2. State Standards • CLE.3203.1.6 – Distinguish between common ionic and covalent compounds • CLE.3202.1.7 – Construct chemical formulas for common compounds • CLE.3202.TE.4 – Describe the dynamic interplay among science, technology, and engineering within living, earth-space, and physical systems

3. 1 – Compounds and Molecules KEY QUESTIONS • What holds a compound together? • How can the structure of chemical compounds be shown? • What determines the properties of a compound?

4. Chemical Bonds • Forces that hold atoms or ions together in a compound are chemical bonds • H and O form bonds when water is formed

5. Chemical Structure • The way that atoms are bonded together to make a compound results in chemical structure • This structure can be shown by various models • Example : Ball and Stick Model

6. Chemical Structure • Some models show bond length and bond angles • Ball and stick • Other models show space occupied by compounds • Space-filling model ( Figure 2 in Chapter 6 – page 178 ) • ETHANOL 

7. Bonds are like SPRINGS • Bonds are flexible and act like springs • Bonds can bend, stretch, compress, and twist • Do this without breaking • Temperature affects this motion ( Kinetic Theory )

8. How Structure Affects Properties • Chemical structure determines properties • Network structures form strong solids • Quartz (network of rigid Si-O-Si bonds ) • Some networks consist of bonded ions • Salt ( NaCl formed from Na+ and Cl- ions ) • Group 1 elements form cations / Group 17 anions • Some compounds are made of molecules • Sugar is a group of single ( the same ) molecules

9. Attractive Forces Vary • Example : H2O • Water is liquid at room temp • Sugar is solid at room temp • Indicates that water has weaker attractive forces

10. Attractive Forces Vary • Forces between molecules • Example : H2O • Water has higher melting point than H2S • Indicates that water has stronger attractive forces

11. 1 – Compounds and Molecules KEY QUESTIONS • What holds a compound together? • How can the structure of chemical compounds be shown? • What determines the properties of a compound?

12. 2 – Ionic and Covalent Bonding KEY QUESTIONS • Why do atoms form bonds? • Why do ionic bonds form? • What do atoms joined by covalent bonds share? • What gives metals their distinctive properties? • How are polyatomic ions similar to other ions?

13. Why do Chemical Bonds Form? • In general, atoms join to form bonds so that each atom may have a stable electron configuration • They want a full level of valence electrons!!

14. Ionic Bonding • Formed from the attraction between ions • Ions are formed by transfer of electrons • Na and Cl form salt • Ionic compounds form as networks • Solids are the result • Ionic compounds dissolved in water conduct electricity

15. Covalent Bonds • These are formed when electrons are SHARED • EXAMPLES : O2, Cl2, N2 • Atoms may share more than one pair of electrons • Atoms do not always EQUALLY SHARE electrons

16. Metallic Bonds • A type of covalent bond • Occurs between metals • Electrons move freely between metal atoms • Metals are flexible and conduct electricity well because their atoms and electrons can move freely throughout the packed structure

17. Polyatomic Ions • Acts as a single unit in a compound, like ions that consist of a single atom do ( like Cl, Na ) • Hydroxide ( OH - ) • NaOH • Carbonate ( CO32- ) • CaCO3 • Ammonium Sulfate : (NH4)2SO4 +1 -2

18. Polyatomic Ions • Some of these are named based on the number of oxygen atoms in compound • Nitrate vs Nitrite • NO3- vs NO2- • Chlorate vs. Chlorite • ClO3- vs ClO2-

19. 2 – Ionic and Covalent Bonding KEY QUESTIONS • Why do atoms form bonds? • Why do ionic bonds form? • What do atoms joined by covalent bonds share? • What gives metals their distinctive properties? • How are polyatomic ions similar to other ions?

20. 3 – Compound Names & Formulas KEY QUESTIONS How are ionic compounds named? What do the numerical prefixes used in naming covalent compounds tell you? What does a compound’s empirical formula indicate?

21. Naming Ionic Compounds • Ionic compounds are named based on the constituent ions • Cations ( + ) are named based on the element • “calcium” • “magnesium”

22. Naming Ionic Compounds • Anions ( - ) are altered names of elements • “oxide” • “chloride”

23. Put ‘Em Together • sodium chloride ( NaCl ) • magnesium chloride ( MgCl2 ) • aluminum oxide ( Al2O3 )

24. Formula Unit • sodium chloride ( NaCl ) • magnesium chloride ( MgCl2 ) • aluminum oxide ( Al2O3 ) • calcium fluoride ( CaF2 ) Wikepedia.org

25. Naming Ionic Compounds • Charge ( + ) of many transition metals varies • Fe may have 2+ or 3+ • Thus, some names show cation charge • iron(III) oxide [common form ] • iron(II) oxide • Can also see charge in chemical formulas • Fe2O3 [ Fe3+ since Oxygen is often O2- ] • FeO [ both ions have a ‘2’ charge ]

26. Naming Covalent Compounds • Numerical prefixes indicate chemical formula when more than atom is involved • Examples: • carbon dioxide ( CO2 ) • silicon dioxide ( SiO2 ) • boron tetrafluoride ( BF3 ) • Dinitrogen tetroxide ( N2O4 ) N2O4 via Wikepedia.org

27. Empirical Formulas • Indicates the smallest whole-number ratio of atoms in a compound • Some are same as chemical formula • Hydrogen Peroxide is exception: • Chemical Formula – H2O2 • Empirical Formula – HO • Formaldehyde, acetic acid, and glucose have same empirical formula

28. Empirical Formula • Molecular Formulas ( had Formula Unit for Ionics ) • Emprirical formula can be determined by analyzing mass of each element in a compound

29. 3 – Compound Names & Formulas KEY QUESTIONS How are ionic compounds named? What do the numerical prefixes used in naming covalent compounds tell you? What does a compound’s empirical formula indicate?