1. A TOMS, B ONDING, AND THE P ERIODIC T ABLE Valence Electrons and Bonding The number of valence electrons (electrons in the outermost energy level) in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.

2. The Periodic Table As the number of protons (atomic number) increases, the number of electrons also increases. As a result, the properties of the elements change in a regular way across a period. The maximum # of outermost electrons an atom can have is eight (even if the energy level could otherwise hold more).

3. Why are noble gases relatively UNreactive? Question:

4. Why are noble gases relatively UNreactive? Question: Their atoms already have eight outermost electrons, so they are stable.

5. Charged Particles Sometimes an atom can gain or lose electrons When the # of electrons is different from the # of protons, then the atom has an electrical charge. These atoms are called ions.

6. - Ionic Bonds Ions and Ionic Bonds When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

7. Ionic Bonds A bond that forms when one atom takes one or more electrons from another atom is called an ionic bond. One atom gains electrons (becomes -); the other atom loses electrons (becomes +). The opposite charges (+/-) attract.

8. Question: Does a negative ion have more protons or more electrons?

9. Question: Does a negative ion have more protons or more electrons? Answer: More ELECTRONS!

10. Ionic Bonding with Sodium and Chlorine

11. - Ionic Bonds Ions and Ionic Bonds Ionic bonds form as a result of the attraction between positive and negative ions.

12. - Ionic Bonds Properties of Ionic Compounds In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.

13. Nomenclature We write ions with their chemical symbol, then with a + or – the number of electrons lost or gained. A “+” charge indicates the # of electrons lost A “-” charge indicates the # of electrons gained.

14. - Ionic Bonds Ions and Ionic Bonds Ions are atoms that have lost or gained electrons.

15. Check Questions Formation of an Ionic Bond Q. What is an ionic bond? A. An ionic bond is the attraction between two oppositely charged ions. Q. What is the overall charge on an ionic compound? A. Overall, an ionic compound is electrically neutral. - Ionic Bonds

16. End of Section: Ionic Bonds

17. Covalent Bonding " My name is Bond… Covalent Bond."

18. Covalent Bonding A bond formed when atoms share electrons Let’s fill in the blanks: An atom wants to fill its outermost energy level with _______ electrons, unless they are the elements _________ or ________, which only want ____.

19. Covalent Bonding A bond formed when atoms share electrons Let’s fill in the blanks: An atom wants to fill its outermost energy level with _eight__ electrons, unless they are the elements _________ or ________, which only want ____.

20. Covalent Bonding A bond formed when atoms share electrons Let’s fill in the blanks: An atom wants to fill its outermost energy level with _eight__ electrons, unless they are the elements _Hydrogen_ or _Helium_, which only want ____.

21. Covalent Bonding A bond formed when atoms share electrons Let’s fill in the blanks: An atom wants to fill its outermost energy level with _eight__ electrons, unless they are the elements _Hydrogen_ or _Helium_, which only want two_.

22. - Covalent Bonds How Covalent Bonds Form The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.

23. - Covalent Bonds How Covalent Bonds Form The oxygen atom in water and the nitrogen atom in ammonia are each surrounded by eight electrons as a result of sharing electrons with hydrogen atoms.

24. - Covalent Bonds How Covalent Bonds Form An oxygen molecule contains one double bond, while a carbon dioxide molecule has two double bonds. A nitrogen molecule contains one triple bond.

25. - Covalent Bonds Unequal Sharing of Electrons Fluorine forms a nonpolar bond with another fluorine atom. In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.

26. - Covalent Bonds Unequal Sharing of Electrons A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. In contrast, a water molecule is a polar molecule because of its bent shape.

27. QuestionAnswer Asking Questions How do covalent bonds form?Covalent bonds form when two atoms share electrons. How does unequal sharing of electrons affect the atoms in molecular compounds? Unequal sharing of electrons causes the bonded atoms to have slight electrical charges. - Covalent Bonds

28. End of Section: Covalent Bonds

29. - Bonding in Metals Metallic Bonding A metal crystal consists of positively charged metal ions embedded in a “sea” of valence electrons.

30. - Bonding in Metals Metallic Properties The “sea of electrons” model of solid metals explains their ability to conduct heat and electricity, the ease with which they can be made to change shape, and their luster.

31. Properties of Metals due to Metallic Bonding Metallic bonding Electrical conductivity Heat conductivity Ductility Malleability Luster Cause Effects - Bonding in Metals

32. End of Section: Bonding in Metals

33. Graphic Organizer Attraction between opposite (+/-) ions FeatureIonic Bond Polar Covalent Bond Nonpolar Covalent Bond Metallic Bond How Bond Forms Charge on Bonded Atoms? Example Unequal sharing of electrons Yes; positive or negative Yes; positive because the electrons are only loosely connected O2O2 Equal sharing of electrons Attraction between positive ions and “sea” of electrons. Yes, slightly positive or slightly negative No Na + Cl - H2OH2O Gold