2.5 – To distinguish between ionic and covalent bonds.

2.6 – To write the molecular formula of various compounds based on the ionic charges

BONDS436

436

An atom or a group of atoms that have gained or lost electrons

(it has a charge)

2 types

CATIONS (positive ions)

ANIONS(negative ions)

These atoms lose electrons

These atoms gain electrons

Ex. Na1+ Ex. Cl1-

1. IONIC BONDS – formed between oppositely charged ions (ex. between a metal vs nonmetal)-forms when electrons are transferred from one atom to another

ExampleNa+1 combined with

Cl-1

NaCl

http://enstrophy.colorado.edu/~mohseni/ASEN5519Spring2004/TypesOfChemicalBonds1.html

1st: Na gives up an electron to Cl2nd: Forming Na+ & Cl-

3rd: Oppositely charged ions attract & form a “bond”

NaCl

Sodium (Na) loses its one valence electron to Chlorine

(Cl)

resulting in

Na Cl

Na Cl

A positively charged Na ion (+1)

A negatively charged Cl ion (-1)

http://www.visionlearning.com/library/module_viewer.php?mid=55

Br

Br

1st: Ca gives up an electron to each Br

2nd: Forming Ca2+ & two Br-

3rd: Oppositely charged ions attract & form a “bond”

Ca

CaBr2

-

-

2+

When compounds formed by ionic bonds are dissolved in water, the solution will conduct electricity

Why? Ions in solution are mobile & carry a

charge, therefore can carry an electric current

2. COVALENT BONDS -forms when electrons are shared between the atoms-usually forms between non-metals or identical atoms or between metalloids & non-metals

Examples

Cl2

H2

CO

http://enstrophy.colorado.edu/~mohseni/ASEN5519Spring2004/TypesOfChemicalBonds1.html

1st: Both Cl have a strong affinity for their valence electrons2nd: So both Cl atoms share

a valence electron

3rd: Forming a “bond”

Cl2 is an example of covalent bonding. The chlorine atoms each share one of their valence electrons,

Their outermost shell is now full (it is stable)

http://wine1.sb.fsu.edu/chm1045/notes/Bonding/Covalent/Bond04.htm

H2 is another example of covalent bonding.The hydrogen atoms each share their valence electron with one

another. Their outermost shell is now full (recall in the first shell there are

only 2 valence electrons!)

1st: Both C & H have a strong affinity for their valence electrons

2nd: So all atoms share their valence electron, forming a “covalent bond”

1st: Both O & H have a strong affinity for their valence electrons

2nd: So all atoms share their valence electron, forming a “covalent bond”

When compounds formed by covalent bonds are dissolved in water, the solution will NOT conduct electricity

Why? There are no ions or free charges present,

so no electricity can be conducted

Which of the following compounds have ionic bonds?

1. MgCl2

2. Al2O3

3. SO2

4. CH4

5. BeF2

6. SiO2

Recall – ionic bonds are formed between a metal & non-metal

Which of the following compounds have covalent bonds?

1. C2H6

2. P2O5

3. NH3

4. Li2S

5. F2

6. AlCl3

Recall – covalent bonds

are formed between non-metals or

metalloid & non-metal

Which of the following compounds when dissolved in water will produce an electrolytic solution?

1. C6H12O6

2. H2S

3. C2H4OH

4. MgCl2

5. AlBr3

Recall – ionic compounds when dissolved in waterwill conduct electricity

Which of the following compounds when dissolved in water will NOT form ions?

1. Fe2O3

2. H2

3. Ca(OH)2

4. MgS

5. NO2

Recall – only ionic compounds when dissolved in water

will form ions

To learn more information on covalent and ionic bonds go to the following websites:

http://www.accessexcellence.org/RC/VL/GG/cov_IonicBs.html

http://www.mse.cornell.edu/courses/engri111/bonding.htm

http://www.dac.neu.edu/physics/b.maheswaran/phy1121/data/ch09/anim/anim0904.htm

A group of elements bonded together to form a single ion with their own charge

Same as ions except they are in groups instead of single atoms

OH_ (hydroxide ion)

•It has a charge of 1-

•Consists of an oxygen atom and a hydrogen atom

•Treated like one single ion even though it is made up of 2 atoms

SO42- (sulfate ion)

•It has a charge of 2-

•Consists of a sulfur atom and four oxygen atoms

http://www.hcc.mnscu.edu/programs/dept/chem/V.12/page_id_23714.html

Charge on ion

How to we write formulas using polyatomic ions???

1. Treat to polyatomic ion as a single item & note the charge (sulfate has a charge of 2-)

Sodium sulfate

2. Note the charge on the other element (sodium (Na) has a charge of 1+)

3. Use the crossover rule to find the formula (Na2SO4)

SO42-Na1+

Na2SO4

1. Treat to polyatomic ion as a single item & note the charge

Magnesium Hydroxide

2. Note the charge on the other element

3. Use the crossover rule to find the formula

OH1-Mg2+

Mg(OH)2

1. Treat to polyatomic ion as a single item & note the charge

Lithium Phosphate

2. Note the charge on the other element

3. Use the crossover rule to find the formula

PO43-Li+

Li3PO4

1. Treat to polyatomic ion as a single item & note the charge

Calcium Carbonate

2. Note the charge on the other element

3. Use the crossover rule to find the formula

CO32-Ca2+

Ca2(CO3)2CaCO3

1. Treat to polyatomic ion as a single item & note the charge

Ammonium bromide

2. Note the charge on the other element

3. Use the crossover rule to find the formula

Br-NH4+

NH4Br

Worksheet # 1 Study guide, Module 3, page 8 and

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