CHEMICAL BONDSChapter 19

Glencoe Physical Science

What atomic particle determines the

chemical properties of an element?

a. protons b. neutrons c. electrons d. morons

Which electrons determine an

element’s chemical properties?

a. electrons near the nucleus of the atom

b. middle energy level(s) c. valence electrons

How many valence electrons do most atoms need to become chemically stable?

a.1b.4c. 8d.10

Atoms are chemically stable (or resistant to change) when their valence shells are completely filled with electrons.

For most atoms, 8 electrons are needed to be chemically stable.

Why do the Noble Gases not form compounds easily?

How are electrons in an atom

represented?

a. Bohr Models b. Lewis Dot Diagrams c. both of these

How are valence electrons in an atom

represented?

a. Bohr Models b. Lewis Dot Diagrams c. both of these

Why do chemical bonds form?

To become stable!!!!(atoms will gain, lose, or share

electrons in order to achieve “Noble Gas configuration.”)

Types of Chemical Bonds

1.Ionic Bonds = usually metal + nonmetal2. Covalent Bonds =

nonmetal + nonmetal

Classify the following compounds as

covalent or ionic:1. NaCl2. CO2

3. H2O

4. MgCl25. C4H10

Classify the following compounds as

covalent or ionic:1. NaCl (ionic)2. CO2

3. H2O

4. MgCl25. C4H10

Classify the following compounds as

covalent or ionic:1. NaCl (ionic)2. CO2 (covalent)

3. H2O

4. MgCl25. C4H10

Classify the following compounds as

covalent or ionic:1. NaCl (ionic)2. CO2 (covalent)

3. H2O

4. MgCl25. C4H10

Classify the following compounds as

covalent or ionic:1. NaCl (ionic)2. CO2 (covalent)

3. H2O (covalent)

4. MgCl25. C4H10

Classify the following compounds as

covalent or ionic:

1. NaCl (ionic)2. CO2 (covalent)

3. H2O (covalent)

4. MgCl2 (ionic)

5. C4H10

Classify the following compounds as

covalent or ionic:1.NaCl (ionic)2.CO2 (covalent)

3.H2O (covalent)

4.MgCl2 (ionic)

5.C4H10 (covalent)

What are ions?

How do ions form?

Ion

an atom that has gained or lost one or more electrons, therefore it has a positive or negative charge

Ionic BondUsually forms between a metal

and a nonmetalIs the force of electrostatic

attraction between positively and negatively charged ions

Ionic Charges are indicated by a

Superscript

superscript -“written above”Examples: Na+, Mg2+, Cl-, O2-

A transfer of electrons takes place

If an atom loses electrons it becomes ____ charged.

If an atom gains electrons, it becomes ____ charged.

A transfer of electrons takes place

If an atom loses electrons it becomes POSITIVELY charged.

If an atom gains electrons, it becomes NEGATIVELY charged.

Metals tend to lose electrons.

Nonmetals tend to gain electrons.

Demonstration of Ionic Bonding

Student Activity 1Groups 1 and 8: Show ionic bonding

between lithium and fluorineGroups 2 and 7: Show ionic bonding

between sodium and fluorineGroups 3 and 6: Show ionic bonding

between potassium and chlorineGroups 4 and 5: Show ionic bonding

between lithium and chlorine

Chemical Formula Indicates the elements in a

compound and the ratio of the atoms of those elements in one unit of the compound.

Chemical Formula• Examples: NaCl; H2O• The “2” in H2O is a subscript.• Subscript (“written

below”)indicates the number of atoms of an element in a unit of that compound.

• What is the ratio of sodium to chlorine in NaCl? hydrogen to oxygen in H2O?

Writing Formulas for Binary Ionic Compounds

Determine the oxidation number of each ion (the number of electrons an atom gains or loses)

Oxidation numbers for the representative elements can be determined from its position on the periodic table. Oxidation Numbers for transition elements are determined from their negative ions.

Writing Formulas for Binary Ionic Compounds

1. Write the symbol of the positive ion first.

2. Write the symbol of the negative ion.3. Add the superscripts. Is the sum zero?4. If the sum does NOT equal zero, criss-

cross the ionic charges. 5. Demonstration and Student Practice

Student Activity 2: Write formulas for

binary ionic compounds

1. lithium & fluorine; magnesium & chlorine2. Sodium & chlorine; calcium & bromine3. potassium & bromine; strontium & chlorine4. potassium & iodine; magnesium & fluorine

DO NOT ERASE the dry erase board!!!!

Check your work:

1.LiF; MgCl22.NaCl; CaBr2

3.KBr; SrCl24.KI; MgF2

Naming Binary Ionic Compounds

1. Write the name of the positive ion first.

2. Write the root of the negative ion’s name.

3. Change the ending to -ide.

Student Activity 3Using the dry erase board, name the

compounds you wrote formulas for in Activity 2

Check your work:

1. Lithium fluoride; magnesium chloride

2. Sodium chloride; calcium bromide

3. Potassium bromide; strontium chloride

4. Potassium iodide; magnesium fluoride

Roman Numerals are used with elements that have more than

one common oxidation number.

(This includes most of the transition

elements)

Examples:CuBr2 is named Copper (II) bromide

PbCl2 is named Lead (II) chloride

EXCEPTIONS: Roman Numerals are NOT needed for silver,

cadmium, and zinc:

These transition elements ALWAYS have the following

oxidation numbers: Ag+ Cd2+, Zn2+

Examples:AgBr is named silver bromide, and

NOT silver (I) bromide, because silver always has a +1 oxidation number.

The same is true for compounds containing Cadmium or Zinc.

Some Special Ions:Copper (I) and (II) = Cu+ and Cu2+

Iron (II) and (III) = Fe2+ and Fe3+

Chromium (II) and (III) = Cr2+ and Cr3+

Lead (II) and (IV) = Pb2+ and Pb4+

Write names for:

1. FeS

2. CuCl

3. PbBr4

Check your work:

1. FeS= Iron (II) sulfide2. CuCl= Copper (I) chloride3. PbBr4 = Lead (IV)

bromide

Write formulas from the following names:

4. Lead (II) bromide5. Chromium (II) sulfide6. copper (II) iodide

Check your work:

4.PbBr2

5.CrS6.CuI2

Binary Ionic Chemical Compounds WS

Write formulas for:1. Sodium bromide2. Calcium chloride3. Magnesium oxide4. Silver chloride5. Iron (III) oxide

Name the following compounds:

6.NaCl7.MgCl28.Al2O3

9.Zn(NO2) 2

10.CuCl2

Check your work!

1. NaBr 6. sodium chloride2. CaCl2 7. magnesium

chloride3. MgO 8. aluminum oxide4. AgCl 9. zinc nitrite5. Fe2O3 10. copper (II) chloride

CW/HWSee “Hand-outs” on class website and

completeWS1WS2