Understanding Chemical Bonds: Ionic, Covalent, and Metallic Bonds

1. Ionic, Covalent, and Metallic Bonds Visit www.worldofteaching.com For 100’s of free powerpoints

2. How Elements Bond 2 Bond Formation • The positive sodium ion and the negative chloride ion are strongly attracted to each other. • This attraction, which holds the ions close together, is a type of chemical bond called an ionic bond. • The compound formed this way is called a salt

3. How Elements Bond 2 Bond Formation • The compound sodium chloride, or table salt, is formed. • A compound is a pure substance containing two or more elements that are chemically bonded.

4. How Elements Bond 2 More Gains and Losses • Can elements lose or gain more than one electron? • The element magnesium, Mg, in Group 2 has two electrons in its outer energy level. • Magnesium can lose these two electrons and achieve a completed energy level.

5. How Elements Bond 2 More Gains and Losses • Some atoms, such as oxygen, need to gain two electrons to achieve stability. • The two electrons released by one magnesium atom could be gained by a single atom of oxygen. • When this happens, magnesium oxide (MgO) is formed.

6. How Elements Bond 2 Convalent Bonds—Sharing • Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult. • The alternative is sharing electrons.

7. How Elements Bond 2 The Convalent Bond • The chemical bond that forms between nonmetal atoms when they share electrons is called a covalentbond. • http://www.youtube.com/watch?v=1wpDicW_MQQ

8. How Elements Bond 2 The Convalent Bond • Shared electrons are attracted to the nuclei of both atoms. • They move back and forth between the outer energy levels of each atom in the covalent bond. • So, each atom has a stable outer energy level some of the time.

9. How Elements Bond 2 The Convalent Bond • The neutral particle is formed when atoms share electrons is called a molecule

10. How Elements Bond 2 The Convalent Bond • A molecule is the basic unit of a molecular compound.

11. Naming Covalent Compounds Remember that ionic compounds are named by saying the name of the first element and then the second element with the ending changed to “ide”: NaCl: sodium chloride MgCl2: magnesium chloride

12. Naming Covalent Compounds Covalent Compounds are also named by stating the name of the first element and then the second changed to “ide”. However, as the elements share electrons and are not charged, we must use prefixes to tell the number of each element in the compound. Ex: H2O dihydrogen monoxide CO carbon monoxide CO2 carbon dioxide

13. Prefixes to Use Mon (o) 1 Oct (a) 8 Di 2 Tri 3 Tetra 4 Pent(a) 5 Hex (a) 6 Hept (a) 7

14. Hydrocarbons Hydrocarbons are covalently bonded molecules with the elements C and H. Hydrocarbons are organic molecules because they have chains of carbons Petroleum compounds are hydrocarbons. Wait, so petroleum and plastics are organic? Yes, by the chemical definition they are.

15. Carbon Forms Chains Each carbon has 4 valence electrons and so can form 4 bonds H O CH3COOH: H-C-C-O-H H H CH4: H-C-H H

16. 4 Molecules of Life Lipids Carbohydrates Protein Nucleic Acids

17. Lipid FAT!!

18. Carbohydrates Can be simple (sugar) or complex (starch) Used for energy

19. Protein Found everywhere in everything Made by the DNA/RNA of cell

20. Nucleic Acid Found in DNA and RNA

21. Molelcular vs Emperical Formulas A molecular formula is the formula as we find it in nature An emperical formula is the lowest whole number formula for a molecule For the emperical formula CH C2H2 acetylene C6H6 benzene