Ionic bonds

According to Gilbert Lewis, atoms combine i order to achieve a more stable electron configuration. Maximum stability is obtained when an atom is isoelectronic with a noble gas. This presentation would enable students to relate lattice energy with physical properties such as melting point.

1. IONIC BONDS Prepared by: Mrs. Eden C. Sanchez

2. Learning Objectives State the Octet Rule. Draw the Lewis dot symbols of atoms and ions. Identify elements that easily form cations and anions based on ionization energies and electron affinities 2

3. Learning Objectives Explain the formation of ionic bonds using electron configuration and the Lewis dot symbols. Relate lattice energy with physical properties of ionic compounds such as melting point. 3

4. Keywords Octet Rule Lewis dot symbol Ionic bond Lattice energy 4

5. Motivation Let them deliver the following statement using the read-aloud protocol: “A chemist named Gilbert Lewis noticed something interesting about elements that were very stable.” 5

6. Motivation 6 Element Atomic No. Electron Configuration Group No. (Old) Group No. (IUPAC) Period No. He 2 1s 2 8A 18 1 Ne 10 1s 2 2s 2 2p 6 8A 18 2 Ar 18 1s 2 2s 2 2p 6 3s 2 3p 6 8A 18 3 Kr 36 1s 2 2s 2 2p 6 3s 2 3p 6 4 s 2 3d 10 4 p 6 8A 18 4 Xe 54 3s 2 3p 6 4 s 2 3d 10 4 p 6 5 s 2 4d 10 5p 6 8A 18 5 Rn 86 4 p 6 5 s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6 p 6 8A 18 6

7. Motivation To what group in the periodic table do these elements belong? These elements are called the noble gases. Why? What is the common characteristic of these gases? Light bulbs are filled with Ar gas rather than oxygen gas. Why? 7

8. Motivation From the electron configuration, how many valence electrons do noble gases have? Can we relate the number of valence electrons with the stability of the element? 8

9. Octet Rule & Lewis Dot Structure According to Lewis, atoms combine in order to achieve a more stable electron configuration maximum stability is attained when an atom is isoelectronic with a noble gas. Except for He, the noble gases have eight outer electrons or an octet of electrons. 9

10. Octet Rule & Lewis Dot Structure Octet Rule states that when atoms of elements combine to form compounds, they tend to lose, gain, or share electrons to achieve the same electron arrangement as the noble gas nearest them in the periodic table. 10

11. Octet Rule & Lewis Dot Structure In combining with other atoms, only outer electrons, the valence electrons , are involved .. The Lewis dot symbol consists of the symbol of an element and one dot for each valence electron in an atom of the element. 11

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13. All elements belonging to the same group have the same number of valence electrons and have the same number of dots around the element symbol. all Group 1A elements have only one valence electron represented by one dot. All Group 7A elements have 7 valence electrons represented by 7 dots. 13

14. Ions Formed from the Representative Elements 14

15. Elements with small ionization energies tend to easily give up electrons to form positive ions or cations . these elements would be the metals particularly those in Groups 1A and 2A. 15

16. The larger the metal atom , the easier it is to lose valence electrons and the more reactive the metal. 16

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18. non-metals have a high tendency to accept electrons and form negative ions, or anions. The smaller the nonmetal atom , the greater the tendency to attract electrons , and the higher the reactivity of the nonmetal . 18

19. Exercises: Give the charge and draw the Lewis dot symbol of the anion formed when a sulphur atom accepts electrons. of the cation formed when a Rb atom loses an electron 19

20. Exercises: of the anion formed when a nitrogen atom accepts electrons of the anion formed when an iodine atom accepts an electron 20

21. IONIC BOND FORMATION Ionic bond is “the electrostatic force that holds ions together in an ionic bond.” Example : formation of the ionic compound, LiF , can be represented using the Lewis dot symbols: 21

22. Exercises: Using the Lewis dot symbol, show the ionic bond formation for Ca 2+ and O 2- or CaO f or Na 2 O For Al 2 O 3 22

23. The Lattice Energy of Ionic Compounds The stability of the ionic compound depends on the strength of the interaction among all the ions in an ionic solid. This stability is measured by the lattice energy of the compound. 23

24. The Lattice Energy of Ionic Compounds The lattice energy is the amount of energy required to completely separate one mole of a solid ionic compound into gaseous ions . 24

25. The Lattice Energy of Ionic Compounds the stronger the interaction among the ions in the ionic compound, the harder to separate them , the larger the lattice energy, the stronger the ionic bond . 25

26. The lattice energy is correlated to the physical properties of ionic compounds such as the melting points . The larger the lattice energy, the harder to separate the ions, the higher the melting point. 26

27. Exercises: Which is expected to have a higher melting point? LiF or NaF ? Arrange the melting points of the following ionic compounds in decreasing order: LiF , LiBr , LiI,and LiCl . Which will have the higher melting point, NaCl or MgO ? Explain. 27

28. Properties of Ionic Compounds Ionic substances form crystalline solids . In the solid state, the ions are in rigid formation in relatively fixed positions in a crystal lattice . This makes them immobile and poor conductors of electricity and heat . 28

29. Properties of Ionic Compounds However, when they melt or are dissolved in solution, they become good electrical conductors. Note, however, that not all ionic solids are soluble in water. Because of the strong electrostatic force of attraction among ions in the solid, they have high melting points and high boiling points. 29

30. Ionic solids are hard and brittle. The electrostatic forces have to be overcome to move the ions and shift them away from one another. 30

31. Ions in the human body Ions play an important role in the body . Calcium, potassium, sodium, chloride , and copper ions are some key ions involved in the electrical events inside the body. Potassium is the major positive ion inside the cell 31

32. Ions in the human body S odium is the major positive ion found in the fluid outside the cell. Ionic chlorine is the most abundant negative ion. 32

33. What will happen to our body if there is an imbalance of any of these ions or certain trace ions in the body? 33

34. Imbalances of any of these ions, certain traces of ions in the body, or inhibition of sodium ion transport across the cell membranes can lead to dysfunction in the conduction of electrical messages . 34

35. This dysfunction quickly leads to a general body disturbance and loss of ability to maintain somewhat stable internal conditions. 35

36. 36 Thank You! Any questions ?

37. CREDITS Special thanks to all the people who made and released these awesome resources for free: Presentation template by SlidesCarnival Photographs by Startup Stock Photos 37