Chemical Bonding

1. Chemical Bonding Preview Section 1 Electrons and Chemical Bonding Section 2 Ionic Bonds Section 3 Covalent and Metallic Bonds Concept Mapping

2. Section1 Electrons and Chemical Bonding Bellringer The following are some very common chemical formulas. C6H12O6 C2H5OH C6H8O6 C6H8O7 Identify the elements in these compounds and predict whether the compounds are similar to each other and why. Record your answers in your science journal.

3. Section1 Electrons and Chemical Bonding Objectives • Describe chemical bonding. • Identify the number of valence electrons in an atom. • Predict whether an atom is likely to form bonds.

4. Section1 Electrons and Chemical Bonding Combining Atoms Through Chemical Bonding • Chemical bonding is the joining of atoms to form new substances. • An interaction that holds two atoms together is called achemical bond. When chemical bonds form, electrons are shared, gained, or lost.

5. Section1 Electrons and Chemical Bonding Combining Atoms Through Chemical Bonding, continued • Discussing Bonding Using Theories and Models We cannot see atoms and chemical bonds with the unaided eye. • So, the use of models helps people discuss the theory of how and why atoms form bonds.

6. Section1 Electrons and Chemical Bonding Electron Number and Organization • The number of electrons in an atom can be determined from the atomic number of the element. • Electrons in an atom are organized in energy levels. • The next slide shows a model of the arrangement of electron in an atom. This model and models like it are useful for counting electrons, but do not show the true structure of an atom.

7. Section1 Electrons and Chemical Bonding

8. Section1 Electrons and Chemical Bonding Electron Number and Organization, continued • Outer-Level Electrons and BondingMost atoms form bonds using only itsvalence electrons,the electrons in an atom’s outermost energy level.

9. Section1 Electrons and Chemical Bonding Electron Number and Organization, continued • Valence Electrons and the Periodic TableYou can use the periodic table to determine the number of valence electrons for atoms of some elements, as shown on the next slide.

10. Section1 Electrons and Chemical Bonding

11. Section1 Electrons and Chemical Bonding To Bond or Not to Bond • The number of electrons in the outermost energy level of an atom determine whether an atom will form bonds. • Atoms that have 8 electrons in their outermost energy level do not usually form bonds. The outermost energy level is considered to be full if it contains 8 electrons.

12. Section1 Electrons and Chemical Bonding To Bond or Not to Bond, continued • Filling the Outermost LevelAn atom that has fewer than 8 valence electrons is more likely to form bonds than an atom that has 8 valence electrons is. Atoms bond by gaining, losing, or sharing electrons to have a filled outermost energy level.

13. Section1 Electrons and Chemical Bonding To Bond or Not to Bond, continued • Is Two Electrons a Full Set?Not all atoms need 8 valence electrons to have a filled outermost energy level. Helium atoms need only 2 valence electrons because the outermost level is the first energy level. • Atoms of hydrogen and lithium form bonds by gaining, losing, or sharing electrons to achieve 2 electrons in the first energy level.

14. Section2 Ionic Bonds Bellringer Historically, salt has had many uses beyond just a spice you put in your soup. Salts are ionic compounds. Brainstorm some uses for salts, things that contain salts, or words and phrases containing the term salt. Where do you think salt comes from? Write your answers in your science journal.

15. Section2 Ionic Bonds Objectives • Explain how ionic bonds form. • Describe how positive ions form. • Describe how negative ions form. • Explain why ionic compounds are neutral.

16. Section2 Ionic Bonds Forming Ionic Bonds • Anionic bondis a bond that forms when electrons are transferred from one atom to another atom. • Charged ParticlesAn atom is neutral because the number of electrons in an atom equals the number of protons. So, the charges cancel each other out. • But when an atom gains or loses electrons, it becomes a charged particle called anion.

17. Section2 Ionic Bonds Forming Positive Ions • Metal Atoms and the Loss of ElectronsAtoms of most metals have few valence electrons and tend to lose these valence electrons and form positive ions. • The Energy Needed to Lose ElectronsEnergy is needed to pull electrons away from atoms. The energy needed comes from the formation of negative ions.

18. Section2 Ionic Bonds Forming Negative Ions • Nonmetal Atoms Gain ElectronsThe outer energy level of nonmetal atoms is almost full. So, nonmetal atoms tend to gain electrons and become negative ions. • The Energy of Gaining ElectronsEnergy is given off when nonmetals gain electrons. An ionic bond will form between a metal and a nonmetal if the nonmetal releases more energy than is needed to take electrons from the metal.

19. Section2 Ionic Bonds

20. Section2 Ionic Bonds Ionic Compounds • When ionic bonds form, the number of electrons lost by the metal atoms equals the number gained by the nonmetal atoms. • The ions that bond are charged, but the compound formed is neutral because the charges of the ions cancel each other.

21. Section2 Ionic Bonds Ionic Compounds, continued • When ions bond, they form a repeating three-dimensional pattern called acrystal lattice,such as the one shown below. • Properties of ionic compounds include brittleness, high melting points, high boiling points, and increase electrical conductivity when dissolved in water solutions.

22. Section3 Covalent and Metallic Bonds Bellringer Brainstorm a list of things made of metal. Record your list in your science journal.Describe three properties of metals based on your list. The use of metal has been key to human technological development. List the types of metal that you use in your everyday life and how you use them. What are the properties of metal that make it useful? What are some of the drawbacks of using metal?

23. Section3 Covalent and Metallic Bonds Objectives • Explain how covalent bonds form. • Describe molecules. • Explain how metallic bonds form. • Describe the properties of metals.

24. Section3 Covalent and Metallic Bonds Covalent Bonds • Acovalent bondforms when atoms share one or more pairs of electrons. • Substances that have covalent bonds tend to have low melting and boiling points and are brittle in the solid state. • Covalent bonds usually form between atoms of nonmetals, such as the atoms shown on the next slide.

25. Section3 Covalent and Metallic Bonds

26. Section3 Covalent and Metallic Bonds Covalent Bonds, continued • Covalent Bonds and MoleculesSubstances containing covalent bonds consist of particles called molecules. Amoleculeusually consists of two or more atoms joined in a definite ratio. • The models on the next slide show two ways to represent the covalent bonds in a water molecule.

27. Section3 Covalent and Metallic Bonds

28. Section3 Covalent and Metallic Bonds Covalent Bonds, continued • One way to represent atoms and molecules is to use electron-dot diagrams. An electron-dot diagram shows only the valence electrons in an atom.

29. Section3 Covalent and Metallic Bonds Covalent Compounds and Molecules • A molecule is the smallest particle into which a covalently bonded compound can be divided and still be the same compound. • The Simplest Moleculesare made up of two bonded atoms. Molecules made up of two atoms of the same element are called diatomic molecules.

30. Section3 Covalent and Metallic Bonds Covalent Compounds and Molecules, continued • More-Complex MoleculesCarbon atoms are the basis of many complex molecules. • Each carbon atom can form four covalent bonds. These bonds can be with atoms of other elements or with other carbon atoms, as shown at right.

31. Section3 Covalent and Metallic Bonds Metallic Bonds • Ametallic bondis a bond formed by the attraction between positively charged metal ions and the electrons in the metal. • Movement of Electrons Throughout a MetalBonding in metals is a result of the metal atoms being so close to one another that their outermost energy levels overlap. This overlapping allows valence electrons to move throughout the metal.

32. Section3 Covalent and Metallic Bonds Metallic Bonding Click below to watch the Visual Concept. Visual Concept

33. Section3 Covalent and Metallic Bonds Properties of Metals • Conducting Electric CurrentMetallic bonding allows metals to conduct electric current. • Electric current is conducted when valence electrons move within a metal. These electrons are free to move because the electrons are not connected to any one atom.

34. Section3 Covalent and Metallic Bonds Properties of Metals, continued • Reshaping MetalsBecause the electrons swim freely around the metal ions, atoms in metals can be rearranged. The properties of ductility and malleability describe a metal’s ability to be reshaped. • Ductility is the ability to be draw in to wires. • Malleability is the ability to be hammered into sheets.

35. Section3 Covalent and Metallic Bonds Properties of Metals, continued • Bending Without BreakingWhen a piece of metal is bent, some of the metal ions are forced closer together. • But the metal does not break because the positive metal ions are always surround by and attracted to the electrons in the metal.

36. Chemical Bonding Concept Mapping Use the terms below to complete the concept map on the next slide. covalent bonds electrons ions metallic bonds molecules chemical bonds

37. Chemical Bonding

38. Chemical Bonding