What is a chemical change? – New substance formed; different properties from the reactants How do we know a chemical reaction has taken place? – (1).

Chemical ChangesChemical Changes

Matter and Chemical ReactionsMatter and Chemical ReactionsMatter and Chemical ReactionsMatter and Chemical Reactions

• What is a chemical change? – New substance formed; different properties from the

reactants

• How do we know a chemical reaction has taken place?– (1). Formation of a gas– (2). Permanent color change– (3). Temperature change

• Exothermic and endothermic – (4). Precipitant formed

• What is a chemical change? – New substance formed; different properties from the

reactants

• How do we know a chemical reaction has taken place?– (1). Formation of a gas– (2). Permanent color change– (3). Temperature change

• Exothermic and endothermic – (4). Precipitant formed

Matter and Chemical ReactionsMatter and Chemical ReactionsMatter and Chemical ReactionsMatter and Chemical Reactions

• How do elements form compounds?– Atoms of the reactant(s) are rearranged and bond in

different combinations

– A + B ----------- C + D

– Phase Changes and Chemical changes Animation

• How do elements form compounds?– Atoms of the reactant(s) are rearranged and bond in

different combinations

– A + B ----------- C + D

– Phase Changes and Chemical changes Animation

Electron ShellsElectron Shells

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley


Note that elements within the same group have the same electron-dot structure. Note that elements within the same group have the same electron-dot structure.

Electron ShellsElectron Shells



• Valence electrons: Electrons in the outermost shell of an atom. These are the ones that can participate in chemical bonding.

• Electron-dot structure: A notation showing the valence electrons surrounding the atomic symbol.

Chemical Bonds Chemical Bonds Chemical Bonds Chemical Bonds • (1). Ionic– Metals transfer electrons to nonmetals– Positive ions (cations) and Negative ions (anions) are

formed

• (2). Covalent– Sharing of electrons between nonmetal atoms – Equal sharing: nonpolar compound– Unequal sharing: polar compound

• (3). Metallic– Sea of electrons float between metal atoms

• (1). Ionic– Metals transfer electrons to nonmetals– Positive ions (cations) and Negative ions (anions) are

formed

• (2). Covalent– Sharing of electrons between nonmetal atoms – Equal sharing: nonpolar compound– Unequal sharing: polar compound

• (3). Metallic– Sea of electrons float between metal atoms

Ionic BondingIonic BondingIonic BondingIonic Bonding

• Characteristics– (1). Electrostatic Attraction between positive and

negative ions– (2). Formation of Crystal Structures– (3). Strong Bonds – High Melting Points – (4). Electrolytes

– Animation

• Characteristics– (1). Electrostatic Attraction between positive and

negative ions– (2). Formation of Crystal Structures– (3). Strong Bonds – High Melting Points – (4). Electrolytes

– Animation

Polar Bonds and Polar MoleculesPolar Bonds and Polar Molecules

• Electronegativity: The ability of a bonded atom to pull on shared electrons. Greater electronegativity means greater “pulling power.”

• Electronegativity: The ability of a bonded atom to pull on shared electrons. Greater electronegativity means greater “pulling power.”



High

Low

Covalent BondingCovalent BondingCovalent BondingCovalent Bonding

• Characteristics• (1). Sharing of electrons between atoms• (2). Electronegativity is similar • (3). Molecules formed • (4). Bonds not as strong as covalent • (5). May be equal or unequal sharing between

electrons• (6). Gases form covalent bonds

• Characteristics• (1). Sharing of electrons between atoms• (2). Electronegativity is similar • (3). Molecules formed • (4). Bonds not as strong as covalent • (5). May be equal or unequal sharing between

electrons• (6). Gases form covalent bonds

The Covalent BondThe Covalent BondThe Covalent BondThe Covalent Bond

• The type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons.




The Covalent BondThe Covalent BondThe Covalent BondThe Covalent Bond


• There are two electrons within a single covalent bond.

• The covalent bond is represented using a straight line.


• There are two electrons within a single covalent bond.

• The covalent bond is represented using a straight line.



F — FF F

Polar Bonds and Polar MoleculesPolar Bonds and Polar MoleculesPolar Bonds and Polar MoleculesPolar Bonds and Polar Molecules

• Electrons within a covalent bond are shared evenly when the two atoms are the same.

• They may be shared unevenly, however, when the bonded atoms are different.

• Electrons within a covalent bond are shared evenly when the two atoms are the same.

• They may be shared unevenly, however, when the bonded atoms are different.




• But if polar bonds within a molecule are facing in equal and opposite directions…

…then the polarity may cancel itself out.












…or not!

More Chemical ReactionsMore Chemical ReactionsMore Chemical ReactionsMore Chemical Reactions

• Animation – Chemistry Comes Alive

• Dust Explosion Animation

• Animation – Chemistry Comes Alive

• Dust Explosion Animation

Metallic BondingMetallic BondingMetallic BondingMetallic Bonding• Characteristics • Electrons of metal atoms flow freely between

other metal atoms• The more mobile the electrons, the better the

electrical conductor• Higher the vibration of electrons more metal is

shiny. • Malleable characteristic due to electrons not

being fixed, but freely flowing • Alloy: White gold (molten gold and palladium are

blended)

• Characteristics • Electrons of metal atoms flow freely between

other metal atoms• The more mobile the electrons, the better the

electrical conductor• Higher the vibration of electrons more metal is

shiny. • Malleable characteristic due to electrons not

being fixed, but freely flowing • Alloy: White gold (molten gold and palladium are

blended)

Metals vs NonmetalsMetals vs NonmetalsMetals vs NonmetalsMetals vs Nonmetals

• High luster, shiny• Malleable • Ductile • High Melting Points • Good Conductors• Poor Insulators

• High luster, shiny• Malleable • Ductile • High Melting Points • Good Conductors• Poor Insulators

• Low luster and dull• Nonmalleable • Not Ductile • Low Melting Points• Poor Conductors • Good Insulators

• Low luster and dull• Nonmalleable • Not Ductile • Low Melting Points• Poor Conductors • Good Insulators

Periodic and Group Trends Periodic and Group Trends

Atomic Size/RadiusAtomic Size/RadiusAtomic Size/RadiusAtomic Size/Radius

Ionization Energy Ionization Energy Ionization Energy Ionization Energy

What is a chemical change? – New substance formed; different properties from the reactants How do we know a chemical reaction has taken place? – (1).

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