Understanding Chemical Bonding: Types, Energy Changes, and Bond Strength

1. BONDING when two nuclei simultaneously attract the same pair of electrons Bond=

2. *The electrons experience a force of attraction from both nuclei. *This_______________________ attraction holds the two particles together. positive-negative-positive *This attraction is called ________________ * a chemical bond. One Pair of Electrons = 1 bond

3. Bonding changes = Energy Changes The ______ the Energy, The More _______ !!!!!!! Lower Stable *Breaking Bonds= Endothermic Endothermic= Absorbing Energy A + B absorbing *By __________ Energy, Atoms become _____ stable when separated. AB less AB + Energy A + B

4. The Lower Remember… _________the Energy, The More_________ !!!!!!!_____________ =____________ Stable High Energy Less Stable • Making Bonds= Exothermic Exothermic = Releasing Energy (Exit, Exhale) When bonds ______, excess energy is ________, resulting in a more ________ compound. Form A+B released stable AB A + B AB + Energy

5. Chemical Energy Potential Energy * ______________ is associated with the changes in bonds between atoms. ( ____________) Stored Energy * Single, uncombined atoms have a _______________ __________ high Potential Energy. *When bonds form, some of the _________________ ______________ Potential Energy is released. * The amount of Potential Energy associated with a specific bond depends on: ______ , ___________, ____________ , etc. Mass Bond Type Atomic Radius

6. Remember the Octet Rule… *Atoms will _____ , _____, or ______ enough electrons as to obtain a _____ , stable octet. lose gain share full A. Electrons can be ______________ Transferred Lost _____ or ______ to form ions with a ______________ = ________________ gained stable octet. IONIC BONDS METALS __________ TO ______________ NON-METALS B. Electrons can be ___________ Shared When _______________ , both atoms feel as if they have a __________. = __________________ sharing electrons full octet Covalent Bonds NON-METAL NON-METAL _____________ TO ________________

7. EXCEPTIONS TO THE OCTET RULE Hydrogen Helium they can only hold a maximum of 2 electrons in their PEL. *_________ and ______ are Exceptions to the octet rule because ___________ ________________________________ ________________________________ *They are stable and Happy :) with a full “ ____” of electrons. duet

8. Are all bonds the same strength? NO!! A. Weak bonds Require little energy to break, and release little energy when forming. (unstable) B.Strong Bonds Require lots of energy to break, and release lots of energy when forming (highly stable)

9. Practice: 1.For the following equation: N(g) + N(g) --> N2(g) + Energy a. Bond broken, energy absorbed b. Bond broken, energy released c. Bonds formed, energy absorbed d. Bond formed, energy is released _____________________________ 2. Which would be true of the reverse reaction? a. Bond broken, energy absorbed

10. More Practice 3. Which amount of energy would be given off in the formation of a highly stable compound? a) -100 kJ/mol b) -800 kJ/mol c) +170 kJ/mol d) +500 kJ/mol ___________________ 4. Which amount of energy from above would symbolize weak bond formed? d) +500 kJ/mol

11. One way to predict bond type is by taking the difference in atom’s electronegativities. What is electronegativity? -Ability to attract electrons Who had the highest electronegativity? Lowest? Highest = Non- Metals,upper right on table Lowest = Metals, lower left corner of table What did an atom’s electronegativity value mean for its reactivity? Higher electronegativity value,more attraction for electrons, Higher reactivity. Lower electro.value, less reactivity. (More on Electronegativity and bonds ahead)

12. Bonds vs. Molecular Attractions BOND Intramolecular Force of Attraction = ________ *When two nuclei simultaneously attract the same pair(s) of electrons to form a covalent bond. (stronger) Intermolecular Force of Attraction *The attraction that exists b/w two separate molecules that is responsible for holding them near one another in space. (weak in comparison)

13. Bond vs Intermolecular forces of attraction

14. Bond Types 1. IONIC 2. METALLIC 3. COVALENT a. nonpolar covalent b. polar covalent c. coordinate covalent

15. Ionic bonds nonmetal metal *Form between a _____ and a _____________ -Metal _____ 1 or more electrons and becomes __ + loses -Nonmetal _____ those electrons and becomes __ gains - *Metal ______(+ ion) attracts Nonmetal _____(anegative ion) = cation Ionic Bonds anion *The amount of electrons transferred depends on how many each atom needs to lose or gain to complete its octet.

16. Ionic bonds

17. NaCl =most common ionic compound Electron Configuration Na Cl 2-8-7 2-8-1 Valence Electrons 1 7 Na Cl Lewis Dot New e- config. With full shell [2-8]+1 [2-8-8]-1 Cl-1 Na+1 Ion Formed * * [ Na ]+1 [ Cl ]-1 * * Lewis Dot of Ion * * * *

18. Ionic Bonding

19. Ionic Bonds can also be predicted using electronegativity values *If the difference in electronegativity is greater than or equal to ______________ ___________ 1.7, the bond is ionic NaCl Cl = Na = 3.2 0.9 2.3= ionic There are exceptions to everything. Remember:

20. Using electronegativity values, predict if the following compounds are ionic. 1) LiBr 2) H2O 3) CaO 4) CO2

21. Properties of Ionic Substances Non metals metals 1.7or higher *Form when ________ react with __________ . *Electronegativity difference of ____________ . *Have ______ melting points and _______ boiling points. *All ionic compounds are _________ at room temperature since the bonds are so _________. *Have very low vapor pressure. high high solids strong -Atoms do not easily go from liquid to gas because of strong bonds.

22. Properties of Ionic Substances *Are ______________ of electricity in the solid state. *Conducts electricity as a _______ or ______. Non conductors liquid aqueous (This allows the electrons to be mobile, move freely and conduct electricity)

23. Writing Lewis Dot Ionic Compounds Na11 Cl17 *In terms of electronegativity values, how can you tell that NaCl is ionic?

24. Writing Lewis Dot Ionic Compounds Use: Ca and F Use: Li and O

25. Binary Ionic Compound: One metal and one nonmetal NaCl, CaBr2, MgO, K2S Some Ionic Compounds have more than 2 elements, they usually contain polyatomic ions NaNO3 CaSO4 AgNO2 NH4Cl LiCr2O7

26. Polyatomic Ions (E) • Grouping of 2 or more atoms that act as a unit and carry a charge. • If a compound contains a polyatomic ion, it has both ionic and covalents bonds. NaNO3 Na+1 and NO3-1

28. Metallic Bonds Metal Metal Are formed between _________ and ____________ -Few valence e- *Metals generally have: -Low ionization energy How much energy is needed to remove the outermost e-) ( Ionization = *Metallic bonds are relatively strong bonds: -Moderately high melting point -Moderately high boiling point

29. Metallic Bonds Nucleus and non valence electrons *Kernel- *Arranged in a fixed position of a crystal lattice move freely about the crystal lattice and do not belong to any given atom. *Valence electrons *Metals are good conductors because of these mobile electrons

30. Metallic Bonds Result from the force of attraction of the mobile valence electrons for an atoms positively charged kernel. *Metallic Bonds ****SEA OF MOBILE ELECTRONS !!! Metal= crystal lattice Red sphere = (+) kernel of metal cations Static = moving e-

31. Examples of Metallic Bonds The bonds found in copper wire The bonds found in a piece of magnesium strip * * * The bonds found in a piece of gold.

32. Properties of metals Composed of Monoatomic metal atoms. Moderate Bond Strength * ex. Cu(s) Au(s) Hg(l) * * * * *Within the metal crystal lattice, electrons belong to the whole crystal rather than individual ions. *Mobility of electrons distinguishes the metallic bonds from all others. Moderate melting and boiling points Conducts electricity in the solid and liquid phase Malleable and ductile

33. MOLECULES Covalent Bonds = shared between 2 or more non metals to obtain a stable octet. *Electrons are -Sharing can be or *Electronegativity difference is usually equal unequal below 1.7 = H2 H H H H * * * * is full for BOTH by SHARING. Outer shell Remember… Hydrogen can have only 2 in its outer shell. By sharing 1 pair of e- = 2 e-

34. Practice Covalent Bonds Combine : F and F Show the formation of H2O

35. Double Bonds 2 Pairs of e- (4 e-) are shared Makes it more stable, Lower Potential Energy *Double Bond- - *Each bond is usually 1 e- from each atom forming the pair. Example: Show the formation of the following: CO2

36. Triple Bonds 3 Pairs of e- (6 e-) are shared between 2 atoms. *Triple Bonds- * Very stable, low Potential Energy Example: N2

37. How many e- are shared? Single Bond: Cl-Cl, H-H _____pairs of e- _____ e- total Double Bond O=O _____ pairs of e- _____ e- total Triple Bond NΞN _____ pairs of e- _____ e- total 1 2 2 4 3 6

38. Polar or Non Polar Covalent?? Polar Non Polar *Each Covalent Bond is one of 2 types: or Non Polar Covalent Bonds: -A bond formed between 2 atoms that have the same attraction ( electronegativity) for the shared pair of e-. - - Equal pull on bonding pair Symmetrical e- charge distribution ***Different non metals can have the same electronegativity values

39. Examples of Non Polar Bonds Examples: Cl2 H2 CS2 C-S H - H Cl - Cl

40. Polar Covalent Bonds *Polar Covalent Bonds: -Bonds formed between 2 non metal atoms which have different attractions for shared e- (different electronegativities) - - - Unequal pull on bonding pair of e- Asymmetrical e- charge distribution Leaves partial charges on atoms within molecule H – Cl

41. Polar Covalent Examples: H2O HBr NH3 e- cluster around more electronegative atom

42. Properties of Covalent Molecules non metal non metal Low low *Form when a _________ reacts with a __________ *Have ____ melting points and ____ freezing points *Molecular solids are soft *Covalent Molecules are ______________ of heat and electricity *Molecular substances are generally _____________ *Molecular substances have a ____ vapor pressure poor conductors weak bonds high (goes into vapor easily because of weak bonds.)

43. Shapes of Molecules the repelling of electrons *The shapes of molecules is determined by _____________ ________________ There are 5 Basic shapes: *Tetrahedral *Linear *Planar *Angular *Pyramidal

44. Linear When there are 2 atoms in a molecule Any molecule in which the bonds cause the atoms to fall in a straight line. H2 C2H2 CO2

45. Angular H2O *V-shaped or Bent SO2 H2S

46. Planar *The atoms of a molecule fall in the same plane. C2H4

47. Pyramidal *3 shared pairs of electrons will cause a pyramid shape. PCl3 NH3

48. Tetrahedral *4 evenly separated bonds CCl4 CH4

49. Polarity Of Molecules *Molecules can either be polar or non polar. (Do not confuse bond polarity with molecular polarity) Bond Polarity- When checking between 2 atoms if there is difference in electronegativity or not. *Polar bond-difference in electronegativity between 2 atoms *Non Polar Bond- No difference in electronegativity between 2 atoms.

50. NonPolar Molecules *Molecules containing only nonpolar covalent bonds, are always nonpolar molecules! All diatomics: Br2,I2,N2 ,Cl2,H2, O2, F2,