1. Chemical Bonding

2. Chemical bonds
_____________________ that hold atoms together in compounds. The electrons involved in bonding are usually those in the _____________________ (valence) shell.
Most elements in compounds want to gain _____________________ configuration. They will do so by either _________________or _________________ electrons (_____________________ compounds) or by __________________ electrons (_____________________ compounds)

3. Ionic and Covalent bonding
Chemical bonds are classified into two types:
_____________________results from electrostatic attractions among ions; which are formed by the transfer of one or more electrons from one atom to another. (metals low χ with nonmetals high χ)
(χ = electronegativity)
_____________________ results from sharing one or more electron pairs between two atoms (nonmetals only similar χ )

4. Comparison of Ionic & Covalent Compounds
Melting Pt
Solubility
(polar solvents)
(nonpolar solvents)
Conductivity
(molten & aqueous solutions)
High Low Soluble Insoluble Insoluble Soluble High Low

5. Ionic vs. Covalent bonding
2 extremes in bonding
_________________ covalent bonds
electrons equally shared by the atoms
_________________ ionic bonds
electrons are completely lost or gained by one of the atoms
most compounds fall somewhere _________________ these two extremes

6. Terminology # of atoms in the molecule
_____________________ = 1 atom Ex. He
_____________________ = 2 atoms Ex. O2
_____________________ = 3 atoms Ex. O3
_____________________ = many Ex. H2SO4 or S8
_____________________ : the mlcl is composed of only 1 kind of atom: O2, H2, P4
_____________________ : the mlcl is made up of more than 1 kind of atom: H2O

7. Lewis Dot Representations of Atoms
or Lewis dot formulas, a convenient bookkeeping method for ____________________ (electrons that are transferred or involved in chemical bonding)
Only the electrons in the outermost s and p orbitals are shown as dots.

8. elements in the same group have same Lewis dot structures
For groups _____________________, the group number equals the # of _____________________ electrons
Valence electrons determine the chemical and physical properties of the elements as well as the kinds of __________________ they form.

9. Ionic Bonding metals react with nonmetals to form ionic compounds
_____________________ or positive (+) ions (metals)
atoms have lost 1 or more electrons
_____________________ or negative (-) ions (nonmetals)
atoms have gained 1 or more electrons

10. We can use Lewis formulas to represent the neutral atoms and the ions they form.

11. underlying reasons for LiF formation
1s s p
Li ­¯ ­
F ­¯ ­¯ ­ ¯ ­¯­
becomes
Li+ ­¯ [He]
F ­¯ ­¯ ­¯ ­¯ ­¯ [Ne]

12. Li+ ions contain two electrons F- ions contain ten electrons
same number as helium
F- ions contain ten electrons
same number as neon
Li+ ions are isoelectronic with _____________________
F- ions are isoelectronic with _____________________
*Isoelectronic species contain the _____________________ number of electrons.
cations become isoelectronic with _____________________ noble gas
anions become isoelectronic with _____________________ noble gas

13. similarly for all of the IIA & VIIA M(s) + X2 ® M2+ X2-
IIA metals with VIIA nonmetals, mostly ionic compounds ~ exceptions - BeCl2, BeBr2, BeI2 these are covalent compounds
Be(s) + F2(g) ® BeF2(s) electronically this is happening
similarly for all of the IIA & VIIA
M(s) X2 ® M2+ X2-

14. SUMMARIZING TABLE Groups Gen. Form. Example
IA + VIIA MX
IIA + VIIA MX2
IIIA + VIIA MX3
IA + VIA M2X
IIA + VIA MX
IIIA + VIA M2X3
NaF
BaCl2
AlF3
Na2O
BaO
Al2S3

15. SUMMARIZING TABLE Groups Gen. Form. Example
IA + VA M3X IIA + VA M3X2 IIIA + VA MX
Na3N
Mg3P2
AlN
H forms ionic compounds with IA and IIA metals (metal hydrides)
LiH, KH, CaH2, BaH2,, etc.
other H compounds are covalent

16. lattice energy
_____________________ - the energy needed to separate oppositely charged ions. It is the energy that converts an ionic solid into widely separated gas ions
The _____________________ the lattice energy, the _____________________ the ionic bond.
The stronger the ionic bond the _____________________ in water at a given temperature, since the ions must _____________________ _____________________ from one another and attach to water in order to dissolve.

17. Coulomb’s Law
_____________________ Law: for electrostatic attraction and/or repulsion. Applies to charged particles, magnets, gravitation, ionization energy, lattice energy
~ ions with high (big)charges = F is large
~ ions with small (little) charges = F is small

18. if opposite charges - The greater (bigger) the charges the greater the _____________________
if like charges - The _____________________ (bigger) the charges the greater the repulsion.
Also the closer the particles are the ________________ the attraction or repulsion will be.

19. When Applying Coulomb’s Law to Ionic Compounds
E = k
Energy = lattice energy,
Q1 = charge of positive ion
Q2 = charge of negative ion
r = bond length, the distance between the nuclei of the 2 ions – can also be _____________________ by the Period.

20. For r (Use the Period of the element that is _____________________ with the ion!
Na is in Period 3 and has 3 occupied energy levels. Na+ has lost an electron. It has 10 electrons and is isoelectronic with Ne in Period 2. Na+ has only 2 occupied energy levels.)

21. arrange these compounds in order of increasing attractions among ions
KCl, Al2O3, CaO

22. 1. Which has a stronger ionic bond, NaCl or KCl. Explain why
1. Which has a stronger ionic bond, NaCl or KCl? Explain why. The lattice energy of ________ is stronger, so this is the stronger ionic bond. Both have an electron charge of -1 and an effective nuclear charge of 1. But the valence electrons of _____ are in the 3rd energy level, leading to a shorter bond length (measured as distance between ionic nuclei) and a stronger ionic bond than ________.

23. 2. Which has a stronger ionic bond, NaCl or AlCl3. Explain why
2. Which has a stronger ionic bond, NaCl or AlCl3? Explain why. The ________ has a stronger ionic bond. Both have the same -1 charge for the chloride ion, and both Na+ and Al+3 are isoelectronic with Ne and therefore have 2 occupied energy levels. But the higher positive charge of the ________ ion leads to a stronger lattice energy and a stronger ionic bond.

24. 3. Which is more soluble in 80° C water, NaCl or KCl
3. Which is more soluble in 80° C water, NaCl or KCl? Explain why You can dissolve more grams of ________ in 100 grams of 80° C water since it has a weaker ionic bond/lattice energy which requires less energy to separate/dissociate the ions from one another and allow them to attach to the polar water molecules.

25. 4. Which is more soluble in 80° C water, NaCl or AlCl3
4. Which is more soluble in 80° C water, NaCl or AlCl3? Explain why ________ is more soluble in 80° C water since it has a weaker ionic bond/lattice energy which requires less energy to separate/dissociate the ions from one another and allow them to attach to the polar water molecules.

26. 5. Why is Na2O considered soluble in water while Al2O3 is not Q2 for oxygen is the same for both compounds, a -2. Radius of oxygen is the same for both, and Na+ and Al+3 are isoelectronic. So the larger Q1 charge of Al+3 makes the lattice energy of the ________ greater, and since the ions stay bonded to one another it will not dissociate and dissolve.

27. Structures of Ionic Compounds
extended three dimensional arrays of oppositely charged ions
_____________________ points because coulomb force is strong

28. Covalent Bonding covalent bonds formed when atoms share electrons
share 2 electrons - ___________________covalent bond
share 4 electrons - ___________________covalent bond
share 6 electrons - ___________________covalent bond
attraction is electrostatic in nature
lower potential energy when bonded

29. Covalent bonding may be explained by 2 different theories (more on this coming soon)
___________________ ___________________(VB) theory: each atom has electrons in atomic orbitals which overlap to form bonds
___________________ ___________________(MO) theory: the electrons belong to the molecule as a whole and are in molecular orbitals instead of belonging to each atom

30. General rules for Lewis Dot Diagrams for Covalent bonds
The element needing the most electrons to fill its octet is usually the central atom
The most symmetrical skeleton is usually correct
Halogens and H always share one electron to complete outer shell
In ternary acids, H are bonded to O (ternary acids are oxy-acids: they contain H, O, and another nonmetal)

31. Carbon always obeys the octet rule
Carbon rarely has lone pairs of electrons. Exception: If it’s at the end of a molecule or ion. Ex. CN- , CO, CNO
When forming multiple bonds between atoms, both atoms donate the same number of electrons

32. Oxygen atoms normally bond to other nonmetals, not to each other
Oxygen can do several things depending on the mlcl.
Single bond by sharing an electron
Single bond by accepting 2 electrons from another atom and not sharing at all
Double bonds by sharing 2 of its electrons

33. Pure covalent bonds - Nonpolar Covalent Bonds
___________________ : diatomic molecules
hydrogen, H2
fluorine, F2
nitrogen, N2
___________________ covalent bonds - electrons are shared equally
symmetrical charge distribution -
must be the ___________________ ______________to
share exactly equally

34. Lewis dot representation
H2 molecule formation

35. Polar Covalent bonds - Unequal sharing of electrons
______________________________: diatomic molecules
hydrogen halides
hydrogen fluoride, HF
hydrogen chloride, HCl
hydrogen bromide, HBr

36. ___________________ bonds - unequally shared electrons
___________________ charge distribution
different ___________________ ___________________
Some bonds are ___________________, Ex. HF

37. Polar Covalent Bonds Electron density map of HF H-F
blue areas
low electron density
red areas
high electron density
polar molecules have separation of centers of negative and positive charge

38. Some bonds are only slightly polar, ex. HI

39. Polar Covalent Bonds Electron density map of HI H-I
blue areas
low electron density
red areas
high electron density
notice that the charge separation is not as ______ as for HF
HI is only slightly polar

41. The Octet Rule
___________________ ___________________ elements achieve noble gas configurations in most of their compounds.
Lewis dot formulas are based on the ___________________.
H needs two electrons to have Helium's noble gas configuration, everything else wants 8

42. Lewis Dot Formulas for Molecules and Polyatomic Ions
water, H2O

43. Lewis Dot Formulas for Molecules and Polyatomic Ions
ammonia molecule , NH3

44. Lewis Dot Formulas for Molecules and Polyatomic Ions
ammonium ion , NH4+

45. Lewis Dot Formulas for Molecules and Polyatomic Ions
hydrogen cyanide, HCN

46. Lewis Dot Formulas for Molecules and Polyatomic Ions
sulfite ion, SO32-

47. Resonance
Two or more Lewis dot diagrams are needed to describe the bonding in a molecule or ion.
LDD for sulfur trioxide, SO3

48. Resonance three possible structures for SO3 invoke resonance
Double-headed arrows are used to indicate resonance formulas.

49. Resonance flaw in our representations of molecules
no single or double bonds in SO3
all bonds are the same length
best picture

50. More Resonance structures
Carbonate, CO3 -2

51. More Resonance structures
Nitrate, NO3 -1

52. More Resonance structures
Nitrite, NO2 -1

53. List of common Resonance structures
Sulfite ion, SO32-
Sulfur trioxide, SO3
Carbonate ion, CO32-
Nitrate ion, NO31-
Nitrite ion, NO21-
*Sulfate ion, SO42-
*Sulfur dioxide, SO2
*Ozone, O3
*Benzene, C6H6

54. Formal Charges
The concept of formal charges helps us choose the correct Lewis structure for a molecule. If a ___________________ ___________________ has a high formal charge it’s not a very good one. A formal charge is assigned to each element in a compound
Formal charge = group # - (e- you can assign
to that atom)
Or F.C. = (valence e- ) – (# of bonds + # of
unshared e- )

55. Let’s assign formal charges for the elements in the L. D. D
Let’s assign formal charges for the elements in the L.D.D. from water, H2O to sulfite ion, SO32-

56. Sigma and Pi bonds
___________________ ___________________(σ) : result of head- on (end to end overlap, there is a free rotation around σ bonds. ___________________ ___________________(π) : result of side- on overlap of p orbitals. There is no free rotation around a π bond. The side –on overlap locks the molecule into place. All ________________ bonds are sigma bonds: 1σ bond All ________________ bonds: 1 σ bond, 1 π bond All ________________ bonds: 1 σ bond, 2 π bonds

57. Limitations of the Octet Rule for Lewis Formulas
species in which the central element must have a share of more or less than 8 valence electrons to accommodate all substituents
compounds of the d- and f-transition metals
In cases where the octet rule does not apply, the elements attached to the central atom nearly always attain noble gas configurations.
The central atom does not

58. Limitations of the Octet Rule for Lewis Formulas
Write LDD for BBr3

59. Limitations of the Octet Rule for Lewis Formulas
Write LDD for AsF5

60. Limitations of the Octet Rule for Lewis Formulas
Write LDD for XeF4