Unit #6 Chemical Bonds / Stoicheometry / Nomenclature Unit #6 Chemical Bonds / Stoicheometry / Nomenclature

Unit #6

Chemical Bonds / Stoicheometry / Nomenclature

Unit #6

Chemical Bonds / Stoicheometry / Nomenclature

Chemical bond - Chemical bond -

A strong attractive force between atoms or ions in a molecule. They can be either ionic or covalent.

A strong attractive force between atoms or ions in a molecule. They can be either ionic or covalent.

Ionic bond - Ionic bond -

A chemical bond formed by the electrostatic attraction between oppositely charged ions. Simply stated: it results from the transfer of electrons.

A chemical bond formed by the electrostatic attraction between oppositely charged ions. Simply stated: it results from the transfer of electrons.

Examples: NaCl, KBr, CaCl2, Fe2O3

Covalent bond - Covalent bond -

Chemical bond formed by the sharing of electrons. Chemical bond formed by the sharing of electrons.

Examples: H2O, CO2, C6H12O6, CH3OH

Remember: the single, double, and triple bonds drawn in unit #5. They were all covalent bonds.

Covalent bonds may be either of two types:

Covalent bonds may be either of two types:

1) Polar covalent -1) Polar covalent -

2) Non-Polar covalent -

A bond between two atoms caused by the "equal" sharing of the bonding electrons.

A bond between two different atoms caused by the unequal sharing of the bonding electrons.

Chemical bonds can occur between:

Chemical bonds can occur between:

Metal : Non-metalMetal : Non-metal (Ionic) Ex: KI, MoS2

Non-metal : Non-metal (Covalent) Ex: O2, N2O

Metals ≠ DO NOT bond with metals.They can form mixtures more commonly called alloys.

Animations of Chemical Bonds

Animations of Chemical Bonds

Types of Chemical Bonds (Ionic, Polar covalent, & Non-polar covalent)Types of Chemical Bonds (Ionic, Polar covalent, & Non-polar covalent)

http://www.glencoe.com/sites/common_assets/science/cmc/cim/animations/ch8_3_1.swf




Make sure that you remember the location of the three different types of elements on the periodic chart

Make sure that you remember the location of the three different types of elements on the periodic chart

Make certain that you remember the three different types of elements on the periodic chart.

Electronegativity - Electronegativity -

The measure of the attraction an atom has for shared electrons. (How much an atom wants electrons.)

The measure of the attraction an atom has for shared electrons. (How much an atom wants electrons.)

Animation of Electronegativity

Animation of Electronegativity

The "Ups and Downs" of ElectronegativityThe "Ups and Downs" of Electronegativity

http://www.glencoe.com/sites/common_assets/science/cmc/cim/animations/ch6_3.mov




Compare the electronegativities of the elements.Compare the electronegativities of the elements.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

How to use electronegativity to predict the type of chemical bond

that will form:


that will form:1) Calculate the difference in

electronegativity between the two elements that are going to bond.

1) Calculate the difference in electronegativity between the two elements that are going to bond.

These values are on the back of your periodic chart, as well as in various chemistry texts.


that will form:


that will form:

The difference is determined by subtracting the smaller number from the larger.

The difference is determined by subtracting the smaller number from the larger.

The element with the larger electronegativity will tend to have possession of (“hog”) the shared electrons more than the other element.


that will form:


that will form:

If the difference is 1.6 or greater; the bond will be ionic.

If the difference is 1.6 or greater; the bond will be ionic.

Example: NaClExample: NaCl

Cl=

Na=

Cl=

Na= 0.93

3.16

2.23 = Ionic Bond


that will form:


that will form:

If the difference is less than 1.6, and 0.4 or greater; the bond will be polar covalent.

If the difference is less than 1.6, and 0.4 or greater; the bond will be polar covalent.

Example: CO2Example: CO2

O=

C

=

O=

C

=2.55

3.44

0.89 = Polar Covalent Bond


that will form:


that will form:

If the difference is less than 0.4; the bond will be non-polar covalent.

If the difference is less than 0.4; the bond will be non-polar covalent.

Example: Cl2Example: Cl2

Cl=

Cl=

Cl=

Cl= 3.16

3.16

0.00 = Non-Polar Covalent Bond

Ionic bondingIonic bonding

Remember definition of an ionic bond:Remember definition of an ionic bond:A chemical bond formed by the

electrostatic attraction between oppositely charged ions. Simply stated: it results from the transfer of electrons.

When do ionic bonds occur?When a metal bonds with a non-

metal or when the difference in electronegativity is 1.6 or greater.

Ionic compound - Ionic compound -

A compound composed of positive

and negative ions. It is always written with the

cation first, the anion second.

A compound composed of positive

and negative ions. It is always written with the

cation first, the anion second.

Ionic compounds dissolve in polar solvents.

Ionic bonding - Ionic bonding -

Occurs when electrons are actually transferred from the outer shell (the valence shell) of one atom or molecule to the outer shell (the valence shell) of another, oppositely charged, atom or molecule.

Occurs when electrons are actually transferred from the outer shell (the valence shell) of one atom or molecule to the outer shell (the valence shell) of another, oppositely charged, atom or molecule. As a result both atoms usually attain filled valence shells with noble-gas configurations. This process of electron transfer is always exothermic.

Ionic bonding can also involve polyatomic ions.Ionic bonding can also involve polyatomic ions.

Polyatomic ion -

An ion composed of 2 or more atoms. The charge is assumed to be on the entire molecule.Example: CO3

-2

(Carbonate) has the -2 charge dispersed over the entire molecule.

This electron is transferred to the Chlorine ion, leaving this shell empty and the chlorine with a full shell.

Na

Cl

1 Sodium ion + 1 Chlorine ion yields 1 Sodium chloride molecule (an ionic compound).

Animation ofIonic vs. Covalent Bonding

Animation ofIonic vs. Covalent Bonding

The Formation of Sodium chloride and Dihydrogen monoxideThe Formation of Sodium chloride and Dihydrogen monoxide

http://www.glencoe.com/sites/common_assets/science/cmc/cim/animations/ch7_1.avi




Properties of ionic compounds:


Most are:Most are:

Crystalline solids

(crystal: molecules, atoms, ions are arranged in a 3-dimensional repeating pattern.)



Most have:Most have:

Very high melting and even higher boiling points.Example:NaCl melts at 8010C, boils at 14130C. Compare

to covalent compounds (polar) NH3: melts at -

77.70C, boils at -330C; (non-polar) O2: melts at -

218.40C, boils at -182.960C.



Most:Most:

Dissolve in polar solvents (Ex: water)



Most:Most:

Conduct electric current when:

In a molten state.

Dissolved in polar solvents (Ex: water).

Quick review of necessary concepts:Quick review of necessary concepts:

Where are the metals located on the periodic chart?

Where are the metals located on the periodic chart?

Where are the non-metals located?

Considering the number of valence electrons an atom has, when does an atom gain or give electron(s)?If an atom "gives" away electrons, what happens to its oxidation state (charge) and what does it become?If an atom "gains" electrons, what happens to its oxidation state (charge) and what does it become?

Example 1: CaExample 1: Ca

How many valence electrons does it have?How many valence electrons does it have?

Does it gain or give electrons?

How many does it give?

2

Gives

2

Example 2: FExample 2: F

How many valence electrons does it have?How many valence electrons does it have?

Does it gain or give electrons?

How many does it gain?

7

Gains

1

Example 3: Gallium & IodineExample 3: Gallium & Iodine

Can you balance the formula created by combining the above two elements?Can you balance the formula created by combining the above two elements?

GaI3

This will lead to the next section: "Stoicheometry".

StoicheometryStoicheometry

Balancing the charges on ions that are forming a molecule so that they add up to zero.

Balancing the charges on ions that are forming a molecule so that they add up to zero.

Balancing chemical equation so the number of particles of reactants is equal to the number of particles of products.

The total electrons gained must equal the number lost.

4 Steps to "balancing" an ionic compound:


Step 1:Step 1:

Write the cation and the anion next to each other, leave some space between them.



Step 2:Step 2:

Write the absolute value of the cation's charge as the subscript to the anion. (If this value is "1", you don't have to write anything.)



Step 3:Step 3:

Write the absolute value of the anion's charge as the subscript to the cation. (If this value is "1", you don't have to write anything.)



Step 4:Step 4:

Write the above determined subscripts in lowest terms.

Write the balanced formulaformed by combining the followingions: K & P

Write the balanced formulaformed by combining the followingions: K & P

Example 1:

Write the balanced formulaformed by combining the followingions: Al & O

Write the balanced formulaformed by combining the followingions: Al & O

Example 2:

Write the balanced formulaformed by combining the followingions: Mo (VI) & O

Write the balanced formulaformed by combining the followingions: Mo (VI) & O

Example 3:

Sometimes, you may have a

formula and you will need to determine the

charge on the cation (this occurs when

naming transition element compounds).

Use the following steps to achieve this

goal:

Transition element Transition element

Elements that have "d"

and "f" sub-levels. (See unit #3 if

necessary to review "d & f

sublevels").

Elements that have "d"

and "f" sub-levels. (See unit #3 if

necessary to review "d & f

sublevels").

Transition Element Stoicheometry:


Step 1:Step 1:

Write the formula, and separate the cation and anion with a cross.



Step 2:Step 2:

Multiply the charge of the anion with the subscript of the anion (this will always be a negative number); and write this number in the lower right corner of the cross.



Step 3:Step 3: Write the absolute value of the number calculated above (in step 2) in the lower left corner of the cross.



Step 4:Step 4: Divide the number calculated in step 3 above by the subscript of the cation. This calculated value is the charge of the cation.



Example 1:Example 1: WS2

W S2



Example 2:Example 2: CrO3

Cr O3



Example 3:Example 3: MoO

Mo O



Example 4:Example 4: MnO2

Mn O2

Nomenclature -Nomenclature -

The naming of chemical compounds.

The naming of chemical compounds.

There are three different sets of rules used to name simple inorganic compounds.

Ionic Nomenclature:Ionic Nomenclature:

The type of ionic compound will determine which set of rules to use.

The type of ionic compound will determine which set of rules to use.

There are two general types of ionic compounds:

Those in which the cation has only one possible charge.

Examples:Examples:

Na, Ca, Mg, Al, Ba

Those in which the cation has more than one possible charge.

Examples:Examples:

Fe, Cr, Cu, Mo, the transition elements.

If the cation has only one possible charge, name as follows:

If the cation has only one possible charge, name as follows:

Cation:Cation: Simply use the entire name of the element. (It will be capitalized).

Anion:

Use the entire name of the element; minus the ending, plus the suffix "-ide". (It will be lower case).

If Polyatomic Cation or Anion:If Polyatomic Cation or Anion:

Use the whole name of the Polyatomic ion. Regardless if cation or anion.

Use the whole name of the Polyatomic ion. Regardless if cation or anion.

Examples:Examples:

Lithium chlorideLithium chlorideLiCl

MgS Magnesium sulfide

BeCl2 Beryllium chloride

KNO3 Potassium nitrate

(NH4)2SO4 Ammonium sulfate

Name this compound:Name this compound:

FeOFeO

If the cation has more than one possible charge, name as follows:

If the cation has more than one possible charge, name as follows:

Simply use the entire name of the element, followed by a roman numeral (in parenthesis) that indicates the charge of the cation. (It will be capitalized).

Simply use the entire name of the element, followed by a roman numeral (in parenthesis) that indicates the charge of the cation. (It will be capitalized).

Cation:

Anion: Same as the all other ionic compounds.

Polyatomic: Same as other ionic compounds.

Examples:

TiO2 Titanium (IV) oxide

Pb(OH)4 Lead (IV) hydroxide

FeSO4 Iron (II) sulfate

FeO Iron (II) oxide

Fe2O3 Iron (III) oxide

Common Naming Nomenclature:


Transition elements with only two oxidation states are sometimes referred to by common names using these endings:

Transition elements with only two oxidation states are sometimes referred to by common names using these endings:

“-ous” for the smaller charge

“-ic” for the larger charge



This system also uses different names for select metals:

This system also uses different names for select metals:

Plumb-Stann-

Cupr-

Ferr-

Lead

Tin

Copper

Iron

Covalent BondingCovalent BondingWhat is a covalent bond?What is a covalent bond?

When do covalent bonds occur?

Chemical bond formed by the sharing of electrons.

When a non-metal bonds with a non-metal or when the difference in electronegativity is less than 1.6.

Covalent molecule - Covalent molecule -

A molecule formed by 2 or more atoms sharing electrons to achieve an octet in their valence shells.

A molecule formed by 2 or more atoms sharing electrons to achieve an octet in their valence shells.

Examples: H2O, C6H12O6, CO2

Covalent bonding Covalent bonding

Occurs when electrons are shared from the outer shell (the valence shell) of one atom with the outer shell (the valence shell) of another. As a result both atoms attain filled valence shells with noble-gas configurations.

Occurs when electrons are shared from the outer shell (the valence shell) of one atom with the outer shell (the valence shell) of another. As a result both atoms attain filled valence shells with noble-gas configurations.

What are the two types of covalent bonds?

What are the two types of covalent bonds?

Polar covalent - Polar covalent - A bond between two different

atoms caused by the unequal sharing of the bonding electrons. If the difference is less than 1.6, and 0.4 or greater; the bond will be polar covalent.Non-Polar covalent -

A bond between two atoms caused by the "equal" sharing of the bonding electrons. If the difference is less than 0.4 ; the bond will be non-polar covalent.

During covalent bonding: all atoms need electrons.

During covalent bonding: all atoms need electrons.

None of them gain or give electrons.

They all share.

Single bond - Single bond -

Created by the sharing of 1 pair of electrons. It is the weakest and longest of covalent bonds.

Created by the sharing of 1 pair of electrons. It is the weakest and longest of covalent bonds.

Double bond - Double bond -

Created by the sharing of 2 pairs of electrons. It is stronger and shorter than a single covalent bond, but weaker and longer than a triple covalent bond.

Created by the sharing of 2 pairs of electrons. It is stronger and shorter than a single covalent bond, but weaker and longer than a triple covalent bond.

Triple bond - Triple bond -

Created by the sharing of 3 pairs of electrons. It is the strongest and shortest covalent bond.

Created by the sharing of 3 pairs of electrons. It is the strongest and shortest covalent bond.

Properties of covalent compounds:Properties of covalent compounds:

Non-metallic:Non-metallic:

O2 and H2O are covalently bonded

1)


Low melting and boiling points:Low melting and boiling points:

Ionic compound NaCl melts at 8010C, boils at 14130C. Compare to covalent compounds (polar) NH3: melts at -77.70C, boils at -330C; (non-polar) O2: melts at -218.40C, boils at -182.960C.

2)


Poor to non-conductors of electricityPoor to non-conductors of electricity

Rubber and plastics are covalently bonded.

3)


Often gaseous, but may be solid, liquid, or gas.Often gaseous, but may be solid, liquid, or gas.

Solid:

4)

Rubber, SiO2

Liquid: Water, Alcohols

Gas: Methane, CO2, NH3

Covalent Nomenclature:Covalent Nomenclature:

Usually, the least electronegative element is written first.

Usually, the least electronegative element is written first.

Examples: CO2, N2O, SO3

Covalent Nomenclature:Covalent Nomenclature:

Prefixes are used to indicate the number of each atom present in the compound.

1 atom = Mono (except when referring to the first element; in this case you will not use a prefix.)

Covalent Nomenclature:Covalent Nomenclature: 2 atoms =

3 atoms =

4 atoms =

5 atoms = 6 atoms =

Di-

Tri-

Tetr-

Pent-

Hex-

7 atoms =

8 atoms =

9 atoms =

10 atoms =

Hept-

Oct-

Non-

Dec-

The first element will be named by using the prefix (indicating the number of atoms) + the elements name.

The first element will be named by using the prefix (indicating the number of atoms) + the elements name.

Example: N2O4 = Dinitrogen

NOTE: DO NOT USE “MONO-” ON THE FIRST ELEMENT !

The second element will be named by using the prefix (indicating the number of atoms) + the element’s name, minus the ending, plus “-ide”.

The second element will be named by using the prefix (indicating the number of atoms) + the element’s name, minus the ending, plus “-ide”.

Example: N2O4 = Dinitrogentetroxide

Binary acid Nomenclature -Binary acid Nomenclature -

Binary acid -Binary acid - An acid composed of only two elements: Hydrogen and usually a halogen.

Named:

Hydro +Halogen name, - ending, + “_ic acid”

Example:Hydrochloric acid, Hydrofluoric acid

Ternary acid Nomenclature -Ternary acid Nomenclature -

Ternary acid -Ternary acid - An acid composed of only three elements: Hydrogen and a polyatomic ion.Named:

Name of Polyatomic ion, “- ate”ending, + “_ic acid”

Example:Carbonic acid, Nitric acid

1. MgI2

2. Strontium phosphide

3. N2O

4. CrO3

5. GaCl3

1. MgI2

2. Strontium phosphide

3. N2O

4. CrO3

5. GaCl3

6. Copper (II) phosphate

7. Calcium nitrate

8. PF5

9. Al2(CO3)3

10. Sodium hydroxide

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Unit #6 Chemical Bonds / Stoicheometry / Nomenclature Unit #6 Chemical Bonds / Stoicheometry / Nomenclature