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Chapter 4 The Structure of Matter How atoms form compounds.

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Presentation on theme: "Chapter 4 The Structure of Matter How atoms form compounds."— Presentation transcript:

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2 Chapter 4 The Structure of Matter How atoms form compounds

3 Compounds Formed when two or more elements combine Formed when two or more elements combine Must make a chemical change Must make a chemical change New properties New properties Atoms from the different elements form bonds Atoms from the different elements form bonds Chemical Bond- the attractive force that holds different atoms or ions together Chemical Bond- the attractive force that holds different atoms or ions together

4 Compounds Every compound has a specific ratio of atoms Every compound has a specific ratio of atoms Written as a chemical formula Written as a chemical formula H 2 O, C 12 H 22 O 12, NaCl H 2 O, C 12 H 22 O 12, NaCl The ratio is the same every time, every where The ratio is the same every time, every where Different ratio means a different compound Different ratio means a different compound

5 Chemical Structure Shows how the atoms are arranged in the compound Shows how the atoms are arranged in the compound How the atoms or ions are connected How the atoms or ions are connected In order to specify where we need In order to specify where we need – Bond length- distance between the nuclei – Bond angle- Angle between atoms (requires two bonds)

6 Models Ball and stick- Ball represents atoms, stick represents bonds Ball and stick- Ball represents atoms, stick represents bonds Easy to see bond angles Easy to see bond angles Structural formulas- drawn with connections between atoms shown. Structural formulas- drawn with connections between atoms shown. H O H H H H COH

7 Models Space-filling – Shows that atoms the right size and in the right place. Space-filling – Shows that atoms the right size and in the right place.

8 C4H9O2NC4H9O2NC4H9O2NC4H9O2N

9 2 Types of structures Networks Networks A large number of atoms, all bonded together A large number of atoms, all bonded together Atoms bonded Atoms bonded Or ions opposite charges Or ions opposite charges

10 Network Solids Many atoms all bonded together Many atoms all bonded together Quartz is SiO 2 Quartz is SiO 2 Major component of rocks. Major component of rocks. Each Silicon bonded to 4 oxygen atoms Each Silicon bonded to 4 oxygen atoms Angle is 109.5º Angle is 109.5º Gives it a strong rigid structure Gives it a strong rigid structure Makes rocks hard. Makes rocks hard. Gives them a high melting and boiling point Gives them a high melting and boiling point

11 Network Solids Ions bond together Ions bond together Opposite charges attract Opposite charges attract All the positives get surrounded by negatives All the positives get surrounded by negatives Get a repeating pattern Get a repeating pattern Rigid Rigid Brittle Brittle High mp and bp High mp and bp

12 Molecules Specific atoms joined together Specific atoms joined together Weaker attractions than ions. Weaker attractions than ions. Low melting and boiling points Low melting and boiling points Things we know as gases and liquids Things we know as gases and liquids Stronger attraction- higher melting and boiling temperatures Stronger attraction- higher melting and boiling temperatures

13 Bonding When the valence electrons interact When the valence electrons interact Atoms react to achieve full outermost energy levels Atoms react to achieve full outermost energy levels Two ways to do this Two ways to do this – Share electrons – Transfer electrons

14 Keeping Track of Electrons Atoms in the same column Atoms in the same column Have the same outer electron configuration. Have the same outer electron configuration. Have the same valence electrons. Have the same valence electrons. Group 1 has 1 valence electrons Group 1 has 1 valence electrons Group 2 has 2 valence electrons Group 2 has 2 valence electrons Group 13 has 3 valence electrons Group 13 has 3 valence electrons Group 14 has 4 valence electrons Group 14 has 4 valence electrons etc etc

15 Helium only has 2 valence electrons

16 Electron Dot diagrams A way of keeping track of valence electrons. A way of keeping track of valence electrons. How to write them How to write them Write the symbol. Write the symbol. Put one dot for each valence electron Put one dot for each valence electron Dont pair up until they have to Dont pair up until they have to X

17 The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up.

18 Write the electron dot diagram for Na Na Mg Mg C O F Ne Ne He He

19 Electron Configurations for Cations Metals lose electrons to fill their outer levels Metals lose electrons to fill their outer levels They make positive ions. They make positive ions.

20 Electron Dots For Cations Metals will have few valence electrons Metals will have few valence electrons Ca

21 Electron Dots For Cations Metals will have few valence electrons Metals will have few valence electrons These will come off These will come off Ca

22 Electron Dots For Cations Ca +2 Metals will have few valence electrons Metals will have few valence electrons These will come off These will come off Forming positive ions Forming positive ions

23 Electron Configurations for Anions Nonmetals gain electrons to fill their outer levels Nonmetals gain electrons to fill their outer levels They make negative ions. They make negative ions.

24 Electron Dots For Anions Nonmetals will have many valence.electrons. Nonmetals will have many valence.electrons. They will gain electrons to fill outer shell. They will gain electrons to fill outer shell. P P -3

25 Stable Arrangements All atoms react to fill their outer levels All atoms react to fill their outer levels Noble gases have full outer energy levels. Noble gases have full outer energy levels. 8 valence electrons. 8 valence electrons. Also called the octet rule. Also called the octet rule. Ar

26 Ionic Bonding Anions and cations are held together by opposite charges. Anions and cations are held together by opposite charges. The bond is formed through the transfer of electrons. The bond is formed through the transfer of electrons. Electrons are transferred to fill their outer levels Electrons are transferred to fill their outer levels

27 Ionic Bonding NaCl

28 Ionic Bonding Na + Cl -

29 Ionic Bonding All the electrons must be accounted for! All the electrons must be accounted for! CaP

30 Ionic Bonding CaP

31 Ionic Bonding Ca +2 P

32 Ionic Bonding Ca +2 P Ca

33 Ionic Bonding Ca +2 P -3 Ca

34 Ionic Bonding Ca +2 P -3 Ca P

35 Ionic Bonding Ca +2 P -3 Ca +2 P

36 Ionic Bonding Ca +2 P -3 Ca +2 P Ca

37 Ionic Bonding Ca +2 P -3 Ca +2 P Ca

38 Ionic Bonding Ca +2 P -3 Ca +2 P -3 Ca +2

39 Ionic Bonding Ca 3 P 2 Formula Unit

40 Properties of Ionic Compounds Crystalline structure. Crystalline structure. A regular repeating arrangement of ions in the solid. A regular repeating arrangement of ions in the solid. Ions are strongly bonded. Ions are strongly bonded. Structure is rigid. Structure is rigid. High melting points- because of strong forces between ions. High melting points- because of strong forces between ions.

41 Crystalline structure

42 Do they Conduct? Conducting electricity is allowing charges to move. Conducting electricity is allowing charges to move. In a solid, the ions are locked in place. In a solid, the ions are locked in place. Ionic solids are insulators. Ionic solids are insulators. When melted, the ions can move around. When melted, the ions can move around. Melted ionic compounds conduct. Melted ionic compounds conduct. First get them to 800ºC. First get them to 800ºC. Dissolved in water they conduct. Dissolved in water they conduct.

43 Metallic Bonds How atoms are held together in the solid metal How atoms are held together in the solid metal Metals hold onto there valence electrons very weakly. Metals hold onto there valence electrons very weakly. Think of them as positive ions floating in a sea of electrons. Think of them as positive ions floating in a sea of electrons.

44 Sea of Electrons Electrons are free to move through the solid. Electrons are free to move through the solid. Metals conduct electricity. Metals conduct electricity.

45 Metals are Malleable Hammered into shape (bend). Hammered into shape (bend). Ductile - drawn into wires. Ductile - drawn into wires.

46 Malleable

47 Malleable Electrons allow atoms to slide by. Electrons allow atoms to slide by.

48 Ionic solids are brittle

49 Strong Repulsion breaks crystal apart. Strong Repulsion breaks crystal apart.

50 Covalent bonds Nonmetals hold onto their valence electrons. Nonmetals hold onto their valence electrons. They cant give away electrons to bond. They cant give away electrons to bond. Still want full outer level Still want full outer level Get it by sharing valence electrons with each other. Get it by sharing valence electrons with each other. By sharing both atoms get to count the electrons toward noble gas configuration. By sharing both atoms get to count the electrons toward noble gas configuration.

51 Covalent bonding Fluorine has seven valence electrons Fluorine has seven valence electrons F

52 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven

53 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons

54 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons

55 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons

56 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons

57 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons

58 Covalent bonding FF Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons Both end up with full energy level Both end up with full energy level

59 Covalent bonding FF 8 Valence electrons Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons Both end up with full energy level Both end up with full energy level

60 Covalent bonding FF 8 Valence electrons Fluorine has seven valence electrons Fluorine has seven valence electrons A second atom also has seven A second atom also has seven By sharing electrons By sharing electrons Both end up with full energy level Both end up with full energy level

61 Single Covalent Bond A sharing of two valence electrons. A sharing of two valence electrons. Only nonmetals and Hydrogen. Only nonmetals and Hydrogen. Different from an ionic bond because they actually form molecules. Different from an ionic bond because they actually form molecules. Two specific atoms are joined. Two specific atoms are joined. In an ionic solid you cant tell which atom the electrons moved from or to. In an ionic solid you cant tell which atom the electrons moved from or to.

62 How to show how they formed Its like a jigsaw puzzle. Its like a jigsaw puzzle. I have to tell you what the final formula is. I have to tell you what the final formula is. You put the pieces together to end up with the right formula. You put the pieces together to end up with the right formula. For example- show how water is formed with covalent bonds. For example- show how water is formed with covalent bonds.

63 Water H O Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

64 Water Put the pieces together Put the pieces together The first hydrogen is happy The first hydrogen is happy The oxygen still wants one more The oxygen still wants one more H O

65 Water The second hydrogen attaches The second hydrogen attaches Every atom has full energy levels Every atom has full energy levels H O H

66 Multiple Bonds Sometimes atoms share more than one pair of valence electrons. Sometimes atoms share more than one pair of valence electrons. A double bond is when atoms share two pair (4) of electrons. A double bond is when atoms share two pair (4) of electrons. A triple bond is when atoms share three pair (6) of electrons. A triple bond is when atoms share three pair (6) of electrons.

67 Carbon dioxide CO 2 - Carbon is central atom ( I have to tell you) CO 2 - Carbon is central atom ( I have to tell you) Carbon has 4 valence electrons Carbon has 4 valence electrons Wants 4 more Wants 4 more Oxygen has 6 valence electrons Oxygen has 6 valence electrons Wants 2 more Wants 2 more O C

68 Carbon dioxide Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short O C

69 Carbon dioxide l Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short O C O

70 Carbon dioxide l The only solution is to share more O C O

71 Carbon dioxide l The only solution is to share more O C O

72 Carbon dioxide l The only solution is to share more O CO

73 Carbon dioxide l The only solution is to share more O CO

74 Carbon dioxide l The only solution is to share more O CO

75 Carbon dioxide l The only solution is to share more O CO

76 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO

77 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

78 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

79 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

80 Another way of indicating bonds Often use a line to indicate a bond Often use a line to indicate a bond Called a structural formula Called a structural formula Each line is 2 valence electrons Each line is 2 valence electrons HHO = HHO

81 Structural Examples H CN C O H H C has 8 electrons because each line is 2 electrons C has 8 electrons because each line is 2 electrons Ditto for N Ditto for N Ditto for C here Ditto for C here Ditto for O Ditto for O

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