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Chapter 7 Ionic Bonding Keeping Track of Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level.

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Presentation on theme: "Chapter 7 Ionic Bonding Keeping Track of Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level."— Presentation transcript:

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2 Chapter 7 Ionic Bonding

3 Keeping Track of Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level. l Valence electrons - The s and p electrons in the outer energy level. l Core electrons -those in the energy levels below.

4 Keeping Track of Electrons l Atoms in the same column l Have the same outer electron configuration. l Have the same valence electrons. l Easily found by looking up the group number on the periodic table. l Group 2A - Be, Mg, Ca, etc.- l 2 valence electrons

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

6 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.

7 Write the electron dot diagram for l Na l Mg lClC lOlO lFlF l Ne l He

8 Electron Configurations for Cations l Metals lose electrons to attain noble gas configuration. l They make positive ions. l If we look at electron configuration it makes sense. l Na 1s 2 2s 2 2p 6 3s valence electron l Na + 1s 2 2s 2 2p 6 -noble gas configuration

9 Electron Dots For Cations l Metals will have few valence electrons Ca

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

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

12 Electron Configurations for Anions l Nonmetals gain electrons to attain noble gas configuration. l They make negative ions. l If we look at electron configuration it makes sense. l S 1s 2 2s 2 2p 6 3s 2 3p valence electrons l S -2 1s 2 2s 2 2p 6 3s 2 3p 6 -noble gas configuration.

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

14 Stable Electron Configurations l All atoms react to achieve noble gas configuration. l Noble gases have 2 s and 6 p electrons. l 8 valence electrons. l Also called the octet rule. Ar

15 Ionic Bonding l Anions and cations are held together by opposite charges. l Ionic compounds are called salts. l Simplest ratio is called the formula unit. l The bond is formed through the transfer of electrons. l Electrons are transferred to achieve noble gas configuration.

16 Ionic Bonding NaCl

17 Ionic Bonding Na + Cl -

18 Ionic Bonding l All the electrons must be accounted for! CaP

19 Ionic Bonding CaP

20 Ionic Bonding Ca +2 P

21 Ionic Bonding Ca +2 P Ca

22 Ionic Bonding Ca +2 P -3 Ca

23 Ionic Bonding Ca +2 P -3 Ca P

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

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

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

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

28 Ionic Bonding Ca 3 P 2 Formula Unit

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

30 Crystalline structure

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

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

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

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

35 Malleable

36 l Electrons allow atoms to slide by.

37 Ionic solids are brittle

38 l Strong Repulsion breaks crystal apart.

39 Alloys l See p203


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