1. Chemistry http://sciencespot.net/

2. s 8 I want you to meet a friend of mine? Bonding, the way atoms are attracted to each other to form molecules, determines nearly all of the chemical properties we see. And, as we shall see, the number “8” is very important to chemical bonding.

3. What are Molecules? Molecules are a combination of atoms bonded together. Bonding determines the chemical properties of the molecule (compound).

4. Ionic Bonding-Being Like the Noble Gases All atoms want to have the same number of electrons as the Noble Gases. The Noble Gases have very stable electron configurations. In order to achieve the same electron configuration as the Noble Gases metal atoms will give up electrons to form positive ions (cations) and non-metal atoms will receive or take additional electrons to become negative ions (anions). IONS are charged particles. N becomes N -3 Al becomes Al +3 Cl becomes Cl - O becomes O -2 Mg becomes Mg +2 Na becomes Na + The positive and negative ions are attracted to each other electrostatically.

5. Opposites Attract!

6. Putting Ions Together Na + + Cl - = NaCl Ca +2 + O -2 = CaONa + + O -2 = Na 2 O Al +3 + S -2 = Al 2 S 3 Ca +2 + N -3 = Ca 3 N 2 Ca +2 + Cl - = CaCl 2 You try these! Mg +2 + F - = NH 4 + + PO 4 -3 = K + + Cl - = Al +3 + I - = Sr +2 + P -3 = Li + + Br - = Sr 3 P 2 AlI 3 MgF 2 (NH 4 ) 3 PO 4 KCl LiBr Not NH 4 ) 3 PO 4

7. The Covalent Bond Atoms can form molecules by sharing electrons in the covalent bond. This is done only among non-metal atoms.

8. Dot Structures-Octet Rule (All atoms want 8 electrons around them.) Valence electrons are those in the outermost orbitals. They are the ones that can form bonds. Lewis came up with a way to draw valence electrons so that the bonding could be determined.

9. Rules to Write Dot Structures 1. Write a skeleton molecule with the lone atom in the middle (Hydrogen can never be in the middle) 2. Find the number of electrons needed (N) (8 x number of atoms, 2 x number of H atoms) 3. Find the number of electrons you have (valence e - 's) (H) 4. Subtract to find the number of bonding electrons (N-H=B) 5. Subtract again to find the number of non-bonding electrons (H-B=NB) 6. Insert minimum number of bonding electrons in the skeleton between atoms only. Add more bonding if needed until you have B bonding electrons. 7. Insert needed non-bonding electrons around (not between) atoms so that all atoms have 8 electrons around them. The total should be the same as NB in 5 above.

10. Let's Try it! 1. S 2. N 3. H 4. B 5. NB 6. E.. H:O:H ●● H O H Water H 2 O 2 x 2 = 4 for Hydrogen 1 x 8 = 8 for Oxygen 4+8=12 needed electrons 8 – 4 = 4 non-bonding electrons 2 x 1 = 2 for Hydrogen 1 x 6 = 6 for Oxygen You have 8 available electrons 12 - 8 = 4 bonding electrons 8 H 12 N 4 B 4 NB - - H:O:HH:O:H.. H:O:H ●●

11. Let's Try it! 1. S 2. N 3. H 4. B 5. NB 6. E.. O::C::O ●● ●● O C O Carbon Dioxide CO 2 1 x 8 = 8 for Carbon 2 x 8 = 16 for Oxygen 8+16=24 needed electrons 16 – 8 = 8 non-bonding electrons 1 x 4 = 4 for Carbon 2 x 6 = 12 for Oxygen You have 16 available electrons 24 - 16 = 8 bonding electrons 16 H 24 N 8 B 8 NB - - O::C::O.... O::C::O ●● ●●

12. Let's Try it! 1.S 2.N 3.H 4.B 5.NB 6.E...... O::C: O: ●● ●● O O C O Carbonate CO 3 -2 3 x 8 = 24 for Oxygen 1 x 8 = 8 for Carbon 24+8=32 needed electrons 24 – 8 = 16 non-bonding electrons 3 x 6 = 18 for Oxygen 1 x 4= 4 for Carbon You have 22 + 2 more available e - 's 24 H 32 N 8 B 16 NB - -.. O::C:O...... O::C: O: ●● ●● O.. :O: 32 - 24 = 8 bonding electrons -2

13. Section A: Complete the chart using a periodic table to help you.

14. Answer these questions: An atom that gains one or more electrons will have a ____________________ charge. An atom that loses one or more electrons will have a ____________________ charge. An atom that gains or loses one or more electrons is called an ____________. A positive ion is called a ______________ and a negative ion is called an _______________. POSITIVE NEGATIVE ION CATION ANION “An-Eye-On” “Cat-Eye-On”

15. What is an ionic bond? Atoms will transfer one or more ________________ to another to form the bond. Each atom is left with a ________________ outer shell. An ionic bond forms between a ___________ ion with a positive charge and a ________________ ion with a negative charge. Example B1: Sodium + ChlorineExample B2: Magnesium + Iodine ELECTRONS COMPLETE METAL NONMETAL

16. Example B3: Potassium + IodineExample B4: Sodium + Oxygen Example B5: Calcium + ChlorineExample B6: Aluminum + Chlorine

17. What is a covalent bond? Atoms ___________ one or more electrons with each other to form the bond. Each atom is left with a ________________ outer shell. A covalent bond forms between two _________________. Example C1: Hydrogen + HydrogenExample C2: 2 Hydrogen + Oxygen SHARE COMPLETE NONMETAL

18. Example C3: Chlorine + ChlorineExample C4: Oxygen + Oxygen Example C5: Carbon + 2 OxygenExample C6: Carbon + 4 Hydrogen