1. Valence Electrons and Ions

2. Valence electrons – electrons that are in the outershell and have the highest energy

3. Electron dot diagram – element symbol surrounded by the valence electrons

4. Atoms are more stable with 8 valence electrons – a full outer shell – like the noble gases ArgonKrypton

5. Atoms form bonds to get a full outer shell and be more stable

6. A chemical bond is the force of attraction that holds atoms together when they gain, lose or share electrons.

7. When an element loses or gains a valence electron it is called an ion. Negative ion – form when an element gains electrons Positive ion – form when an element loses electrons

8. Octet Rule Atoms gain or lose electrons to have 8 in the outer shell Elements with more than 4 valence electrons – gain electrons Elements with less than 4 valence electrons – lose electrons to get to a full outer shell Fluorine IonFluorine Atom

9. What are the ions that form from Na (sodium), Mg (magnesium), S(sulfur), and F(Fluorine)? NaMgSF Write your answers in your notebook and check them with your table partner.

10. Metals tend to lose electrons in chemical reactions forming positive ions. LiBe NaMg KCa RbSr CsBa FrRa Li + Be 2+ Na + Mg 2+ K + Ca 2+ Rb + Mg 2+ Cs + Sr 2+ What is the ion that forms when lithium loses an electron? What ion does beryllium form? What ion does sodium form? What ion does magnesium form?

11. Nonmetals tend to gain electrons in chemical reactions forming negative ions. OF SCl SeBr TeI What is the ion that forms when oxygen gains two electrons? What ion does Fluorine form? What ion does Sulfur form? What ion does Chlorine form?

12. Ionic and Covalent Bonds

13. What can atoms do when forming chemical bonds? Gain, lose or share electrons

14. When sodium and chlorine bond, a valence electron is transferred to fill the outer shell of chlorine. Sodium goes down to a full outer shell as well.

15. Sodium loses an electron and becomes the sodium ion, Na +1. Chlorine gains an electron and becomes the chlorine ion, Cl -1.

16. Ionic bond – the attraction between two oppositely charged ions Metals bond with nonmetals Ex. NaCl LiBr

17. Ionic compound – made up of positive and negative ions that balance to make a neutral compound Positive ionNegative ion Ionic Compounds Li 1+ F 1- Mg 2+ O 2- Na 1+ Cl 1- Ca 2+ Br 1- K 1+ O 2-

18. Properties of Ionic Compounds Form hard, brittle crystals Strong bond High melting points Conduct electric current when dissolved in water or melted

19. Covalent bond- bond that involves the sharing of electrons Forms between two or more nonmetals 1 molecule of CH 4 – methane gas

20. Covalent Bonds Sharing Electrons By sharing 2 electrons in a covalent bond, each fluorine atom gains a stable set of 8 valence electrons. Which are the shared electrons that form a covalent bond between the 2 fluorine atoms?

21. Why do elements form covalent bonds? To become more stable by having a full outer shell of electrons Which elements form covalent bonds? Nonmetals bonding with nonmetals

22. Properties of Covalent Compounds Form weaker bonds Low melting points Do not conduct electric current when dissolved in water

23. 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 _________. Word bank: negativeionpositive

24. Atoms will transfer one or more ________________ to another to form a 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. Word bank: full nonmetal electrons metal

25. Potassium + IodineSodium + OxygenIodine + Iodine Hydrogen + ChlorineCalcium + ChlorineAluminum + Chlorine Label each pair of elements as ionic or covalent.

26. Potassium + IodineSodium + OxygenIodine + Iodine Hydrogen + ChlorineCalcium + ChlorineAluminum + Chlorine Label each pair of elements as ionic or covalent.

27. Counting Atoms

28. MgCl 2 Chemical Formulas- group of symbols that shows the ratio of elements in a compound subscript Chemical symbols Subscripts – tells ratio of elements in a compound

29. Chemical Formulas H 2 O 1 oxygen atom 2 hydrogen atoms Subscript always goes with the chemical symbol before it. If there is no subscript, there is always 1 atom of that element.

30. Chemical Formulas Coefficient – The number before the chemical formula, means that each type of atom is multiplied by that number 2H 2 O 2 oxygen atoms 4 hydrogen atoms

31. Common nameChemical Formula# AtomsTotal Atoms SugarC 12 H 22 O 11 C-12 H- 22 O-11 45 SaltNaClNa- Cl- Baking sodaNaHCO 3 Na- H- C- O- Laughing gasN2ON2ON- O- Carbon dioxideCO 2 C- O- Chemical Formulas Practice

32. Identify the elements in the following: 3Na 2 SO 4 Na: S: O: 4SrCO 3 Sr:C:O:

33. 3Be 3 (SO 4 ) 2 2Ca(OH) 2 4Al 2 (PO) 4 1 – Multiply everything in the parenthesis by the number outside them 2 – Multiply everything by the coefficient