ionic compounds chapter 8. how do the infinite number of compounds that we see in the world around...

Ionic Compounds Chapter 8

How do the infinite number of compounds that we see in the

world around form from the 92 naturally occurring

elements?

Forming Chemical Bonds

CHEMICAL BONDS

The force that holds two atoms together. Chemical bonds form from the attraction between the protons and electrons in covalent bonds. In

ionic bonds the attraction is between the positive and negative

ions involved.

1. What is a chemical bond?

Valence electrons

2. What do we call the outermost electrons involved in chemical bonding?

They are useful to show valence electrons and to show how two or more

atoms may bond.

3. What are some ways that electron dot diagrams are used?

A measure of how easily an electron can be removed.

4. What is ionization energy?

A measure of the attraction an atom has for electrons.

5. What is electron affinity?

Where do we find high ionization energy and high electron affinity?

Halogens

Where do we find high ionization energy and high electron affinity?

Where do we find high ionization energy and low electron affinity?

Noble gases

Where do we find high ionization energy and low electron affinity?

Where do we find low ionization energy and low electron affinity?

Alkali metals

Where do we find low ionization energy and low electron affinity?

6. Why do we have these differences in reactivity?

The most stable electron configuration is a full valence shell. Atoms will gain lose or share electrons in order to follow the octet rule.

6. Why do we have these differences in reactivity?

Atoms tend to gain lose or share electrons in order to acquire a full valence shell. This is usually 8 valence electrons. Hydrogen and helium only have 2.

7. What is the octet rule?

Formation of Positive Ions

When an atom loses one or more electrons.

8. When does a positive ion form?

Cation

9. What do we call a positively charged ion?

They are all cations, but they show a lot of variation. The cations of the metals can have various charges.

10. What types of ions do transition metals form?

Pseudo-noble gas configuration. For example, Zn will form an ion with a +2 charge [Ar] 3d10

11. What do we call the stable electron configuration that transition metals take that does not resemble the noble gases?

Formation of negative ions

Nonmetals tend to gain electrons.

When an atom gains electrons.

12. When does a negative ion form?

anion

13. What do we call a negatively charged ion?

The cation is the name of the element with the word ion added.The anion is the name of the element with the ending changed to –ide.

14. When an atom becomes an ion its name changes. How do the names of ions differ from the atom from which they were formed?

For example; Sodium becomes Sodium ion.Chlorine becomes Chloride.

Section 2: The Formation and Nature of Ionic Bonds

A bond formed between oppositely charged ions.

15. What is an ionic bond?

Because of the electrostatic attraction between oppositely charged ions.

16. Why do ionic bonds form?

If the ionic bond includes oxygen as its nonmetal anion it is an oxide. Most other ionic compounds create a salt from a metallic cation and a non-metalic anion.

17. What type of ionic compounds are formed from ionic bonds?

An ionic compound that contains only two elements. i.e., NaCl KI MgO Na2O

18. What is a binary ionic compound?

The number of electrons gained by the non-metal must equal the number of electrons lost by the metal.

19. All ionic compounds are neutral. What does that mean with regard to the number of electrons gained or lost?

Properties of Ionic Compounds

Ionic crystals are formed when the positive and negative ions are packed into a regular repeating pattern that balances the forces of attraction and repulsion between ions.

20. What are ionic crystals?

NoLarge numbers of positive and negative ions exist together in a crystal lattice.

21. Do ionic compounds exist as single units?

A three dimensional geometric arrangement of particles. The crystal lattice causes ionic crystals to vary in size and shape due the sizes and relative numbers of ions in the crystal lattice arrangement.

22. What is a crystal lattice?

1.) high melting point2.) tend to be hard3.) tend to be brittle4.) In the solid state, ionic compounds are not good conductors of electricity.5.) In aqueous solutions they are good conductors of electricity.

23. Because ionic bonds are very strong, ionic compounds tend to have certain properties.

Note- When dissolved in water ionic compounds disassociate into positive and negative ions (cations and anions) This allows the ions to move freely. Dissolved ionic compounds are very good conductors of electricity.

An ionic compound whose aqueous solutions conduct an electric current.

24. What is an electrolyte?

In a chemical reaction if energy is absorbed the reaction is endothermic. If the energy is released the reaction is exothermic.

25.

The formation of ionic compounds from cations and anions is always exothermic.

26.

The energy required to separate one mole of ions in an ionic compounds.

27. What is lattice energy?

The stronger the forces holding the ions together the more negative the lattice energy. A very negative lattice energy means the ions are held together very forcefully. Continued

28. What is reflected in the lattice energy?

* Smaller ions generally have more negative values because the nucleus of the cation is closer to the electrons of the anion. continued

28 continued

*The ionic bond formed between ions with larger positive or negative values have more negative lattice energies.

28 continued

MgO which would be formed from Mg+2 and O2- is held together more strongly than NaCl formed from Na+ and Cl -.

28 continued

The chemical formula and the name for the compound must be understood universally. A set of rules is used in naming compounds that will universally allow everyone to write the correct formula when given the name and to write the name of the compound when given the formula.

Section 3:

The simplest ratio of the ions represented in an ionic compound. For example in KBr there is one K+ for every one Br_.

29. What is a formula unit?

The total number of electrons gained by the non-metallic atom(s) must be equal to the number of electrons lost by the metallic atom(s) The overall charge on the formula unit must be zero.

A one atom ion.

Determining charge30. What is a monatomic ion?

1A- 1+2A- 2+5A (15) 3 -

6A (16) 2 -

7A (17) 1 -

The charge on a monatomic ion can be determined by the family

the element is in.

It is not as easy to determine the charge on a transition metal because they vary in charge and one element can often form more than one cation by losing electrons from the s and d orbitials.

The charge on the monatomic ion and equals to number of electrons transferred from one atom on the element to form the ion. The oxidation numbers are used to determine the formula for the ionic compound they form.

31. What is an oxidation number?

A method used to determine the formula for an ionic compound. The symbol for the cation is always written first. continued

32. What is the criss cross method?

1st write the symbol and charge for each ion. • 2nd the numerical charge

for each ion becomes the subscript for the other ion.


For example magnesium nitride: Mg+2N-3

Becomes Mg3N2


Ions made up of more than one atom. The charge on a polyatomic ion applies to the entire group of atoms.

33. What are polyatomic ions?

The subscripts of a polyatomic ion are NEVER changed.If more than one polyatomic ion is needed use parentheses.

33. What are polyatomic ions?

a.) Ammonium and chlorideb.) sodium and phosphatec.) Potassium and acetated.) Magnesium and acetatee.) calcium and phosphatef.) Sodium and nitrateg.) Calcium and chlorateh.) Aluminum and carbonate

Practice

a.) Ammonium and chloride NH4Clb.) sodium and phosphate Na3PO4

c.) Potassium and acetate KC2H3O2

d.) Magnesium and acetate Mg(C2H3O2)e.) calcium and phosphate Ca3(PO4)2

f.) Sodium and nitrate NaNO3

g.) Calcium and chlorate Ca(ClO3)2

h.) Aluminum and carbonate Al2(CO3)3

Practice

i.)potassium and chromate j.)magnesium and carbonate

Practice

i.)potassium and chromate K2CrO4

j.)magnesium and carbonate MgCO3

Practice

A polyatomic ion composed of an element usually a nonmetal bonded to one or more oxygen atoms.

Most polyatomic ions are oxyanions.34. What is an oxyanion?

• The ion with more oxygen atoms is named with the suffi x –ate.

• continued

35. These oxyanions are named with these general conventions:

• * The ion with fewer oxygen atoms is named using the root of the nonmetal with the suffi x –ite.

35. These oxyanions are named with these general conventions:

• * The oxyanion with the greatest number of oxygen atoms is named using the prefix per-, the root of the nonmetal and the suffi x –ate.

36. The four oxyanions formed from the group 7A elements follow these conventions.

• The oxyanion with one less oxygen is named with the root of the nonmetal and the suffi x –ate.


• The oxyanion with two fewer oxygen atoms is named using the root of the nonmetal plus the suffi x –ite.


• The oxyanion with three fewer oxygen atoms is named with the prefix hypo- the root of the nonmetal and the suffi x –ite.


Naming Ionic Compounds.

• 1. Name the cation first and the anion second.

37. You will use the following rules in naming ionic compounds.

• 2. Monatomic cations- use the element name without changing it.

• i.e., sodium chloride


• 3. Monatomic anions- take the name of the element and change the ending to –ide.

• i.e., sodium chloride.


• 4. Some metals have more than one oxidation number( some of the transition metals and families 13 and 14) The name of a compound with those compounds use a roman numeral to indicate the charge on the metal.


• Iron II oxide is FeO• Iron III Oxide is Fe2O3


• 5. If the compound conatins a polyatomic ion simply use the name of the polyatomic ion. Ammonium Chloride NH4Cl.


• A. ) NaBr• B.) CaCl2

• C.) KOH• D.) Cu(NO3)2

• E.) Ag2CrO4

Practice

• A. ) NaBr – Sodium bromide

• B.) CaCl2- Calcium chloride• C.) KOH- Potassium

hydroxide• D.) Cu(NO3)2 Copper II Nitrate• E.) Ag2CrO4 Silver Chromate

Practice

• Determine the cation and anion of the formula

• ↓• Does the cation have

only one oxidation number?

38. How to name ionic compounds ( Flow Chart)

• ↓• Yes. • Write the name of the

cation and then the name of the anion.


• ↓• No.• Write the name of the

cation followed by the roman numeral to represent charge then write the name of the anion.


• Metals do form ionic bonds, but they often form lattices in the solid state.

Section 4: Metallic Bonds and Properties of Metals

• This model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons.

39. What is the elctron sea model?

• In metals the outer energy levels of the metal atoms overlap. The electrons present in the outer energy levels are not held by any specifi c atom and can move easily from one atom to the next.

39. What is the elctron sea model?

• Electrons that are free to move.

40. What are delocalized electrons?

• The attraction of a metallic cation for delocalized electrons. Each ion is bonded to all neighboring metal cations by a the “sea” of valence electrons.

41. What is a metallic bond?

• High melting point and boiling point is the result of all cations being bonded to the “sea” of electrons. All of the attractive forces make it diffi cult to separate one atom from another.

42. Explain the physical properties of metals by metallic bonding.

• Metals are malleable because the particles can be pushed or pulled past one another.


• Metals are good electrical conductors because the delocalized electrons can transfer charge.


• Good conductors of heat because the delocalized electrons can transfer heat energy form one place to another.


• Metals have luster because the delocalized electrons interact with the light absorbing and releasing photons of energy.


Metal AlloysDue to the nature of metallic bonds, it is relatively easy to introduce other elements into a metallic crystal.

• A mixture of elements that has metallic properties.

43. What is an alloy?

• Alnico Al Ni Co Fe• Brass Cu Zn• Cast Iron Fe C• Dental Amalgam Hg Ag Sn• Gold Au Ag Cu• Lead Shot Pb As

A

• Pewter Sn Sb Pb• Stainless Steel Fe Cr Ni• Sterling Silver Ag Cu

43. What is an alloy?

• When the elements involved are either similar in size or when the atoms of one element are considerably smaller that the other.

44. When do alloys most commonly form?

• Substitutional and interstitial.

45. What are the two basic types of alloys?

• The metal atoms are of similar size.

46. What is a substitutional alloy?

• When the metal atoms of one element are considerably smaller than the other. These alloys tend to be strengthened. The smaller atoms act like sand in gravel.

47. What is an interstitial alloy?