I. Introduction to Bonding

1. I. Introduction to Bonding Ch. 6- Chemical Bonding

2. Vocabulary • Chemical Bond • attractive force between atoms or ions that binds them together as a unit • Involve valence electrons • bonds form in order to… • decrease potential energy (PE) • increase stability

3. Types of Bonds • Ionic bonding- results from electrical attraction between large numbers of cations and anions • Usually occurs between metal and nonmetal • Covalent Bonding- results from the sharing of electron pairs between two atoms • Usually occurs between 2 nonmetals

4. Types of Covalent Bond • Nonpolar Covalent Bond • e- are shared equally • symmetrical e- density • usually identical atoms (diatomic molecule) • The seven diatomic molecules are Bromine, Iodine, Nitrogen, Chlorine, Hydrogen, Oxygen, and Fluorine. BrINClHOF (pronounced Brinkle-hoff)

5. - + Types of Covalent Bond cont… • Polar Covalent Bond • e- are shared unequally • asymmetrical e- density • results in partial charges (dipole) • Intermediary between ionic and pure covalent bonds

6. Ionic Bonding Click below to watch the Visual Concept. Visual Concept

7. Covalent Bonding Click below to watch the Visual Concept. Visual Concept

8. Ionic or Covalent? • Most bonds are a blend of ionic and covalent characteristics. • Difference in electronegativity determines bond type. • Greater electronegativity difference more ionic

9. Electronegativity Trend • Attraction an atom has for a shared pair of electrons. • Increases up and to the right.

10. Chemical Bonding, continued • Sample Problem A • Use electronegativity values listed in Figure 20 from the previous chapter in your book, on page 161, and Figure 2 in your book, on page 176, to classify bonding between sulfur, S, and the following elements: hydrogen, H; cesium, Cs; and chlorine, Cl. In each pair, which atom will be more negative?

11. Sample Problem A Solution The electronegativity of sulfur is 2.5. The electronegativities of hydrogen, cesium, and chlorine are 2.1, 0.7, and 3.0, respectively. In each pair, the atom with the larger electronegativity will be the more-negative atom. Chemical Bonding, continued Bonding between Electroneg. More-neg- sulfur and difference Bond type ative atom hydrogen 2.5 – 2.1 = 0.4 polar-covalent sulfur cesium 2.5 – 0.7 = 1.8 ionic sulfur chlorine 3.0 – 2.5 = 0.5 polar-covalent chlorine

12. Visual Concept https://www.youtube.com/watch?v=NgD9yHSJ29I

13. Click below to watch the Visual Concept. Visual Concept https://www.youtube.com/watch?v=PVL24HAesnc

14. Day 2 6-2 Covalent Bonding

15. Covalent Bonds & Molecular Compounds • Molecule- neutral group of atoms that are held together by covalent bonds • A chemical compound whose simplest units are molecules is called a molecular compound • The composition of a compound is given by its chemical formula

16. Formation of a Covalent Bond The electron of one atom and proton of the other atom attractone another. The two nuclei and two electrons repeleach other. These two forces cancel out to form a covalent bond at a length where the potential energy is at a minimum.

17. Characteristics of the Covalent Bond * The distance between two bonded atoms at their minimum potential energy is the bond length. * In forming a covalent bond, atoms release energy. The same amount of energy must be added to separate the bonded atoms. * Bond energy is the energy required to break a chemical bond and form neutral isolated atoms.

18. Characteristics of the Covalent Bond * When two atoms form a covalent bond, their shared electrons form overlapping orbitals. * This achieves a noble-gas configuration. * The bonding of two hydrogen atoms allows each atom to have the stable electron configuration of helium, 1s2.

19. The Octet Rule *Noble gas atoms are unreactive because their electron configurations are especially stable. This stability results from the fact that the noble-gas atoms’ outer s and p orbitals are completely filled by a total of eight electrons. *Other atoms can fill their outermost s and p orbitals by sharing electrons through covalent bonding. *Such bond formation follows the octet rule: Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest energy level.

20. Xe 2s 2p Electron-Dot Diagrams • show valence e- as dots • Core e- are not shown • distribute dots like arrows in an orbital diagram O

21. Lewis Structures • Formulas in which atomic symbols represent electrons • Resonance- bonding molecules that cannot be correctly represented by a single Lewis structure

22. Vocabulary • Single bond- covalent bond produced by sharing one pair of e- (total of 2) • Double bond- covalent bond produced by sharing of two pairs of e- (total 4) • Triple bond-covalent bond produced by sharing 3 pairs of e- (total 6)

23. Lewis Structures Click below to watch the Visual Concept. Visual Concept https://www.youtube.com/watch?v=a8LF7JEb0IA

24. Day 4 • Comparing Bonds

25. Ionic Bonding and Compounds • Ionic compound composed of positive and negative ions combined so positive and negative charges equal • Most ionic compounds exist as crystalline solids. • A crystal of any ionic compound is a three-dimensional network of positive and negative ions mutually attracted to each other. The crystal structure of an ionic compound depends on: *sizes of the cations and anions. *ratio of cations to anions.

26. Ionic Compounds, continued • Formula unit • Lattice energy- energy released when 1 mol of ionic compound is formed (strength)

27. Ionic Vs. Covalent Bonding

28. Polyatomic Ions Certain atoms bond covalently with each other to form a group of atoms that has both molecular and ionic characteristics. A charged group of covalently bonded atoms is known as a polyatomic ion.

29. Vocabulary ION 2 or more atoms 1 atom Polyatomic Ion- charged group of covalently bonded atoms Monatomic Ion Na+ NO3-

30. Types of Bonds • Forces that hold ions together in ionic cmpds is very strong (attraction btwn positive and negative charges) • Covalent bonds are strong, but forces of attraction are much weaker • This difference causes different properties

31. Properties of Bonds COVALENT IONIC e- are transferred from metal to nonmetal e- are shared between two nonmetals Bond Formation Type of Structure true molecules crystal lattice Physical State liquid or gas solid Melting Point low high Solubility in Water yes usually not yes (solution or liquid) Electrical Conductivity no Other Properties Hard but brittle odorous C. Johannesson

32. Metallic Bonding • Bond results from attraction between metal atoms and surrounding sea of electrons • Excellent electrical conductors in solid state • b/c of high mobile valence electrons

33. Types of Bonds METALLIC e- are delocalized among metal atoms Bond Formation Type of Structure “electron sea” Physical State solid Melting Point very high Solubility in Water no yes (any form) Electrical Conductivity malleable, ductile, lustrous Other Properties C. Johannesson

34. Section4 Metallic Bonding Chapter 6 Properties of Metals: Electrical and Thermal Conductivity Click below to watch the Visual Concept. Visual Concept https://www.youtube.com/watch?v=QXT4OVM4vXI