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

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Presentation on theme: "The Structure of Matter Section 1 – Compounds and Molecules Section 2 – Ionic and Covalent Bonding Section 3 – Compound Names and Formulas."— Presentation transcript:

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 – Distinguish between common ionic and covalent compounds CLE – 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 ) – Have to break network to split up Some networks consist of bonded ions – Salt ( NaCl formed from Na + and Cl - ions ) – Group 1 elements form cations / Group 17 anions Some materials are made of separate structures – Sugar is a group of single ( the same ) molecules – Can pull out single molecules unlike with a network

9 Attractive Forces Vary Example : H 2 O 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 : H 2 O Water has higher boiling point than H 2 S 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 : O 2, Cl 2, N 2 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 ( CO 3 2- ) – CaCO 3 Ammonium Sulfate : (NH 4 ) 2 SO

18 Polyatomic Ions Some of these are named based on the number of oxygen atoms in compound Nitrate vs Nitrite – NO 3 - vs NO 2 - Chlorate vs. Chlorite – ClO 3 - vs ClO 2 -

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 ( MgCl 2 ) aluminum oxide ( Al 2 O 3 )

24 Formula Unit sodium chloride ( NaCl ) magnesium chloride ( MgCl 2 ) aluminum oxide ( Al 2 O 3 ) calcium fluoride ( CaF 2 ) 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 – Fe 2 O 3 [ Fe 3+ since Oxygen is often O 2- ] – 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 ( CO 2 ) – silicon dioxide ( SiO 2 ) – boron tetrafluoride ( BF 3 ) – Dinitrogen tetroxide ( N 2 O 4 ) N 2 O 4 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 – H 2 O 2 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?


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