2. Groups - Review Each column is called a “group” Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. Except for He, it has 2 electrons The electrons in the outer shell are called “valence electrons” www.chem4kids.com

3. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

4. Lewis Structures 1.Find # of valence electrons for the element 2.Write the chemical symbol for the element 3.Place 1 dot per valence electron around the elements counter clockwise (fill up singly before doubling) 4.Each side of the element can only have two dots, because each orbital can only hold 2 electrons 5.Lone electrons tell you how many bonds will form 1 dot = 1 electron

5. Lewis Structures 1)Write the element symbol. 2)Carbon is in the 4 th group, so it has 4 valence electrons. 3)Starting at the right, draw 4 electrons, or dots, counter- clockwise around the element symbol. Electron Configuration 1s 2, 2s 2, 2p 2

6. Examples 1.Li 2.Al 3.S 4.Kr How many bonds will they form?

7. Learning Check A. X would not be the electron dot structure for 1) Na2) K3) Al B. X would not be the electron dot formula 1) B2) N3) P

8. Vocabulary zChemical Bond yattractive force between atoms or ions that binds them together as a unit

9. Vocabulary zIonic Bond yBond formed between two ions by the transfer of electrons

10. Properties of Ionic Bonds 1.When a metal (+) and a non-metal (-) combine 2.Oppositely charged ions attract 3.Soluble in water 4.Conducts electricity when dissolved

11. Learning Check A. Number of valence electrons in aluminum 1) 1 e - 2) 2 e - 3) 3 e - B. How will aluminum get an octet 1) lose 3e - 2) gain 3 e - 3) gain 5 e - C.Ionic charge of aluminum 1) 3- 2) 5- 3) 3 +

12. Vocabulary zCovalent Bond yBond formed by the sharing of electrons

13. Covalent Bond Found to the right of the staircase Between 2 non metals of similar electronegativity. electronegativity – the tendency for an atom to attract electrons to itself when it is chemically combined w/another element Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC

14. Bond Polarity Difference in electronegativity determines bond type -- Above 1.7 = ionic –0.3-1.7 = polar covalent –0-0.3 = non-polar covalent Look at periodic table in CRM (p 12). Find the difference between the two #’s (positive #) Which is more polar covalent? (Larger # = more polar) O-O or O-H

15. Bonds in the polyatomic ions and diatomics molecule are all covalent bonds

16. Vocabulary zNonpolar Covalent Bonds yWhen electrons are shared equally H 2 or Cl 2

17. Vocabulary zPolar Covalent Bonds yWhen electrons are shared but shared unequally H 2 O

19. Vocabulary zMetallic Bonds yBond found in metals; holds metal atoms together very strongly yGood conductors at all states. yLustrous yVery high melting points

20. Metallic Bond * Metals do NOT combine with metals. They form alloys which is a solution of a metal in a metal. Examples are steel, brass, and bronze Metallic bonds are referring to the bonds between the atoms of a single metal