1. Chapter 6 Ionic Bonds and Some Main-Group Chemistry

2. I ONIC B ONDING Occurs in ionic compound Results from transferring electron Created a strong attraction among the closely pack compound

3. I ONS AND THEIR CONFIGURATION Na Na + Mg Mg 2+ Cl Cl - O O 2-

4. I ONS AND T HEIR E LECTRON C ONFIGURATIONS - 2 e - - 3 e - Fe: [Ar] 4s 2 3d 6 Fe 2+ : Fe 3+ : [Ar] 3d 6 [Ar] 3d 5 IonsAtoms Mn: Mn 2+

5. I ONIC R ADII

7. I ONIZATION E NERGY Ionization Energy ( E i ) : The amount of energy necessary to remove the highest-energy electron from an isolated neutral atom in the gaseous state.

8. I ONIZATION E NERGY Increasing Ei Decreasing Ei

9. I ONIZATION E NERGY Boron has a lower E i due to a smaller Z eff (shielding by the 2 s electrons)

10. I ONIZATION E NERGY Oxygen has a lower E i since the first electron is removed from a filled orbital

11. H IGHER I ONIZATION E NERGIES M 3+ + e - M 2+ + energy M 1+ + e - M + energy M 2+ + e - M 1+ + energy

12. E LECTRON A FFINITY Electron Affinity ( E ea ) : The energy released when a neutral atom gains an electron to form an anion.

13. I ONIC B ONDS AND THE F ORMATION OF I ONIC S OLIDS Na 1+ Na 1 s 2 2 s 2 2 p 6 Cl+ 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3s13s1 3p53p5 1 s 2 2 s 2 2 p 6 1 s 2 2 s 2 2 p 6 3 s 2 Cl 1-

15. T HE O CTET R ULE Octet Rule : Main-group elements tend to undergo reactions that leave them with eight outer-shell electrons.

16. T HE O CTET R ULE

17. Chapter 7 Covalent Bond and Molecular Structure

18. T YPES OF C HEMICAL B ONDS Bonds: a force that holds groups of two or more atoms together and makes them function as a unit Required 2 e- to make a bond Bond energy: amount of energy required to form or to break the bond

19. T HE O CTET R ULE Metals tend to have low E i and low E ea. They tend to lose one or more electrons. Nonmetals tend to have high E i and high E ea. They tend to gain one or more electrons. Octet Rule : Main-group elements tend to undergo reactions that leave them with eight outer-shell electrons.

20. T HE C OVALENT B OND Covalent Bond : A bond that results from the sharing of electrons between atoms.

22. P OLAR C OVALENT B ONDS : E LECTRONEGATIVITY Electronegativity : The ability of an atom in a molecule to attract the shared electrons in a covalent bond.

23. P OLAR C OVALENT B ONDS : E LECTRONEGATIVITY NaCl HCl Cl 2

24. P OLAR C OVALENT B ONDS : E LECTRONEGATIVITY

25. P OLARITY Polar covalent bonds – the bonding electrons are attracted somewhat more strongly by one atom in a bond Electrons are not completely transferred More electronegative atom: δ-. (δ represents the partial negative charge formed) Less electronegative atom: δ+

26. R ELATIONSHIP B ETWEEN E LECTRONEGATIVITY AND B OND T YPE Predicting bond polarity Atoms with similar electronegativity (Δ EN <0.4) – form nonpolar bond Atoms whose electronegativity differ by more than two (Δ EN > 2) – form ionic bonds Atoms whose electronegativity differ by less than two (Δ EN < 2) – form polar covalent bonds

27. E XAMPLES For each of the following pairs of bonds, choose the bond that will be more polar a.H-P, H-Cb.N-O, S-O

28. L EWIS S TRUCTURES represents how an atom’s valence electrons are distributed in a molecule Show the bonding involves (the maximum bonds can be made) Try to achieve the noble gas configuration

29. E XAMPLES Draw Dot Lewis structure for the following atoms: Na Mg C S Co Chap ter 6/29 Copyright © 2008 Pearson Prentice Hall, Inc.

30. R ULES FOR MULTIPLE ATOMS Duet Rule: sharing of 2 electrons E.g H 2 H : H Octet Rule: sharing of 8 electrons Carbon, oxygen, nitrogen and fluorine always obey this rule in a stable molecule E.g F 2, O 2 Bonding pair: two of which are shared with other atoms Lone pair or nonbonding pair: those that are not used for bonding

31. E LECTRON -D OT S TRUCTURES

33. R ULES FOR W RING D OT L EWIS STRUCTURE Step 1: Calculate the total number of valence electrons of all atoms in the molecule Step 2: Create a skeletal structure using the following rules: Hydrogen atoms (if present) are always on the “outside” of the structure. They form only one bond The central atom is usually least electronegative. It is also often unique (i.e,. the only one atom of the element in the molecule). Remember, there might be no “central” atom. Connect bonded atoms by line (2-electron, covalent bonds

34. R ULES Step 3: Place lone pairs around outer atoms (except hydrogen) so that each atom has an octet Step 4: Calculate the number of electrons you haven’t used. Subtract the number of electrons used so far, including electrons in lone pair and bonding pairs, from the total in Step 1. Assign any remaining electrons to the central atom as lone pair

35. R ULES Step 5: If the central atom is B (boron) or Be (beryllium), skip this step If the central atom has an octet after step 4, skip this step If the central atom has only 6 electrons, move a lone pair from an outer atom to form a double bond between outer atom and the central atom If the central atom has only 4 electrons, do Step 5a to two different outer atoms (i.e, form two double bonds) or twice to one outer atom (i.e., form one triple bond)

36. E LECTRON -D OT S TRUCTURES OF P OLYATOMIC M OLECULES Total valence electrons Step 4: Dot Lewis structure Step 1: Step 2: Draw an electron-dot structure for CF 4. Draw its skeletal

37. E XAMPLES Give the Lewis structure for the following H 2 O CO 2 BH 3 NH 4 + NO 3 -,