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Chemical Bonds. I. Why Atoms Combine Chemical Formulas Chemical Bonds Stability. 1 oxygen atom. 2 hydrogen atoms. A. Chemical Formula. Shows: 1) elements in the compound 2) ratio of their atoms. H 2 O. B. Chemical Bond.

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Chemical bonds

Chemical Bonds

I. Why Atoms Combine

Chemical Formulas

Chemical Bonds

Stability


A chemical formula

1 oxygen atom

2 hydrogen atoms

A. Chemical Formula

  • Shows:

    1) elements in the compound

    2) ratio of their atoms

H2O


B chemical bond
B. Chemical Bond

  • Strong attractive force between atoms or ions in a molecule or compound.

  • Formed by:

    • transferring e- (losing or gaining)

    • sharing e-


C stability

Ne

C. Stability

  • Octet Rule

    • most atoms form bonds in order to have 8 valence e-

    • want a full outer energy level

    • like the Noble Gases

  • Stability is the driving force behind bond formation!


C stability1
C. Stability

  • Transferring e-

  • Sharing e-


Chemical bonds1

Chemical Bonds

II. Kinds of Chemical Bonds

Ionic Bond

Covalent Bond

Comparison Chart


A ionic bond
A. Ionic Bond

  • Attraction between 2 oppositely charged ions.

    • Ions are charged atoms.

    • A cation is a positively charged ion (Forms when an atom loses an e-)

      Formed by metals.

    • An anion is a negatively charged ion (Forms when an atom gains an e-)

      Formed by nonmetals.

    • Ions are formed by transferring e- from a metal to a nonmetal.


A ionic bond1

NaCl

A. Ionic Bond

  • ions form a 3-D crystal lattice


B covalent bond
B. Covalent Bond

  • Attraction between neutral atoms.

    • formed by sharing e- between two nonmetals


B covalent bond1

Cl2

H2O

NH3

B. Covalent Bond

  • covalent bonds result in molecules


B covalent bond2
B. Covalent Bond

  • Nonpolar Covalent Bond

  • e- are shared equally

  • usually identical atoms


B covalent bond3

-

+

B. Covalent Bond

  • Polar Covalent Bond

  • e- are shared unequally between 2 different atoms

  • results in partial opposite charges


C comparison chart
C. Comparison Chart

IONIC

COVALENT

shared between nonmetals

transferred from metal to nonmetal

Electrons

high

low

Melting

Point

Soluble in

Water

usually not

yes

yes (solution or liquid)

Conduct Electricity

no

molecules, odorous liquids & gases

crystal lattice of ions, crystalline solids

Other

Properties

Metal and Nonmetal

Nonmetal ONLY

Types of Elements


Both types of bonds
Both types of bonds

  • Some compounds have a mixture of ionic and covalent bonds.

  • These generally contain POLYATOMIC IONS.

  • Polyatomic ions are groups of non-metal elements bonded covalently together that have an overall charge.

  • Generally polyatomic ions will form an ionic bond with metal.

  • They are easy to recognize because they have three or more elements in the compound.

  • Examples: Na3PO4, Al2(SO3)3


Practice
Practice

What type of compound is shown or described below?

NaCl

CO2

H2O

Fe2O3

Ga(C2H3O2)3

High melting point

Liquid or Gas

Doesn’t dissolve in water

Ionic

Covalent

Covalent

Ionic

Polyatomic (Both)

Ionic

Covalent

Covalent


Chemical bonds2

Chemical Bonds

III. Naming Molecular Compounds

Molecular Names

Molecular Formulas


A molecular covalent names
A. Molecular (Covalent) Names

  • Write the names of both elements.

  • Change the final ending to -ide.

  • Add prefixes to indicate subscripts.

  • Only use mono- prefix with second element.


PREFIX

mono-

di-

tri-

tetra-

penta-

hexa-

hepta-

octa-

nona-

deca-

SUBSCRIPT

1

2

3

4

5

6

7

8

9

10

Covalent Naming Prefixes


A molecular names
A. Molecular Names

  • CCl4

  • N2O

  • SF6

  • carbon tetrachloride

  • dinitrogen monoxide

  • sulfur hexafluoride


B molecular formulas
B. Molecular Formulas

  • Write the more metallic element first.

  • Add subscripts according to prefixes.


B molecular formulas1
B. Molecular Formulas

  • phosphorus trichloride

  • dinitrogen pentoxide

  • dihydrogen monoxide

  • PCl3

  • N2O5

  • H2O


B molecular formulas2
B. Molecular Formulas

  • The Seven Diatomic Elements

  • Br2 I2 N2 Cl2 H2 O2 F2

In nature, these elements are never alone!


Chemical bonds3

Chemical Bonds

IV. Naming Ionic Compounds

Oxidation Number

Ionic Names

Ionic Formulas


A oxidation number
A. Oxidation Number

  • The charge on an ion.

  • Indicates the # of e- gained/lost to become stable.

1+

0

2+

3+

4+

3-

2-

1-


Oxidation chart
Oxidation Chart

-2

-1

-3

0

+3

+1

+2

+/-4


B ionic names
B. Ionic Names

  • Write the names of both elements, cation first.

  • Change the anion’s ending to -ide.

  • If there is a polyatomic ion, write the name of the polyatomic ion.


B ionic names1
B. Ionic Names

  • NaBr

  • Na2CO3

  • SnCl4

  • sodium bromide

  • sodium carbonate

  • tin chloride


C ionic formulas
C. Ionic Formulas

  • Write each ion. Put the cation first.

  • Overall charge must equal zero.

    • If charges cancel, just write the symbols.

    • If not, crisscross the charges to find subscripts.

  • Use parentheses when more than one polyatomic ion is needed.

  • Roman numerals indicate the oxidation #.


Writing ionic formulas
Writing Ionic Formulas

  • Crisscross method.

  • If the charges don’t balance, the number of the charge becomes the subscript for the opposite element or polyatomic ions.

  • Example

  • The charges BALANCE thus disappear.

Mg +2 N-3

= Mg3N2


Writing formulas
Writing Formulas

  • Example 2: Al+3 SO4-2

    • Remember to use parentheses when more than one polyatomic ion is needed.

    • Al2(SO4)3

  • Example 3: Na+1 C2H3O2-1

    • NaC2H3O2

    • Remember If charges cancel, just write the symbols.


C ionic formulas1
C. Ionic Formulas

  • potassium chloride

  • magnesium nitrate

  • aluminum oxide

  • K+ Cl- KCl

  • Mg2+ NO3-  Mg(NO3)2

  • Al3+ O-2 Al2O3


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