ionic compounds: formation - florida state universityzakarian/az_personal_web_cz/chm1050... · some...

Compounds: Introduction to Bonding

Most elements exist as compounds in combination with

other elements

Compounds are formed by an exchange of electrons

Two types of compounds:

• Ionic: as a result of transferring electrons

• Covalent: as a result of sharing electrons

Ionic Compounds: Formation

Ions: charged particles formed from atoms or groups of

atoms

Cations (+): positively charged ions (i.e. from metals)

Anions (-): negatively charged ions (i.e. from non-metals)

Ionic “bonding” is a result of electrostatic attraction

E ! charge(1)"charge(2)distance

All elements want to be like noble gases

that is, to have the same number of electrons

(the same electronic configuration)

Example: Sodium Chloride, NaCl, Na+Cl- :

Na(11 electrons) - 1 e- = Na+ (10 electrons); like Ne

Cl (17 electrons) + 1 e- = Cl- (18 electrons); like Ar




Main group elements:

Group 1 alkali metals: lose one electron # M+

Group 2 alkaline earth metals: lose two electrons # M2+

Group 3 metals: lose three electrons # M3+




Main group elements:

Group 7 halogens: acquire one electron # A-

Group 6 elements: acquire two electrons # A2-

Group 5 elements: acquire three electrons # A3-


But a continuous network of ions

Ionic Compounds: Structure

NO bonds in solid or liquid state

NaCl

Covalent Compounds:

Real Bonds

Simplest case: Hydrogen

H• + H• = H:H = H2 compare to He:

Non-metals SHARE electrons to attain the nearest

noble gas electron count (electronic configuration).

Covalent Compounds:

Real Bonds

Another example: Oxygen

O: + O: = O::O = O2 compare to Ne





Covalent Compounds:

Real Bonds

More complex example: Oxygen and Hydrogen

H• + •O• + •H = H:O:H = H-O-H = H2O

Key Distinction

Covalent Compounds Are Molecules

ionic compounds do not have molecules

(solid or liquid)

Polyatomic Ions

hydroxide OH–

sulfate SO4

2–

nitrate NO3

–

phosphate PO4

3–

carbonate CO3

2–

bicarbonate HCO3

–

dichromate Cr2O

7 2–

perchlorate ClO4

–

permanganate MnO4

–

acetate CH3CO

2–

Common Anions Common Cations

ammonium NH4

+

hydronium H3O

+

and metalsFe2+ iron (II) or ferricFe3+ iron (III) or ferrousCu+ copper (I) or cupricCu2+ copper (II) or cuprous

Chemical Formulas

empirical formula shows the relative number

of atoms in a compound; derives from the masses of

the component elements - elemental analysis

Acetic acid CH2O

molecular formula shows the actual number of

atoms in a compound

Acetic acid C2H4O2 or (CH3CO2H)

(extended)

Chemical Formulas:

Structural

structural formula is the most comprehensive

representation of a compound, defines completely the

number of atoms and their connectivity

H

C

H

CH

O

O

H

Acetic acid, C2H4O2 (CH3CO2H):

Structural

formula

Chemical Formulas:

Molecular

(NH4)2HPO4 = N2H9PO4

Ca3(PO4)2 =

Ce(NH4)2(NO3)6 =

Chemical Formulas:

Molecular


Ca3(PO4)2 = Ca3P2O8

Ce(NH4)2(NO3)6 =

Chemical Formulas:

Molecular


Ca3(PO4)2 = Ca3P2O8

Ce(NH4)2(NO3)6 = CeN8H8O18

Some Nomenclature

! In ionic compounds, the cation goes first, the anion follows

i.e. ammonium phosphate (NH4+)3PO4

3–

! Metal cations: the same as the name of the metal

i. e. lithium # lithium chloride LiCl; lead # lead (II) iodide PbI2

! Monoatomic anions: root + -ide

i.e. chlorine # lithium chloride; oxygen # titanium oxide TiO2

! Polyatomic anions: oxoanions with more O root + ate,

otherwise root + ite

i.e. sulfate (SO42–) sulfite (SO3

2–); nitrate (NO3–) nitrite (NO2

–)

Some Nomenclature:

Acids! Polyatomic anions are formed from acids

anion ends with -ate; acid ends with -ic

anion ends with -ite; acid ends with -ous

NO3- nitrate HNO3 nitric acid

SO42- sulfate H2SO4 sulfuric acid

PO43- phosphate H3PO4 phosphoric acid

SO32- sulfite H2SO3 sulfurous acid

CO32- carbonate H2CO3 carbonic acid

! Binary acids:

hydrofluoric acid HF

hydrochloric acid HCl

hydrobromic acid HBr

hydroiodic acid HI

Some Nomenclature:

Binary Covalent Compounds

! In the same period, the element on the left side is the first

word in the name; if in the same period, the element with the

higher period number (lower in the periodic table) goes first

!The second element: root + ide

! Only If more than one element present in the first word,

there is a greek numerical prefix to indicate the number of

atoms. The second element usually has a prefix.

Some Nomenclature:

Binary Covalent Compounds

CO carbon monoxide

CO2 carbon dioxide

SO3 sulfur trioxide

S2Cl2 disulfur dichloride

Cl2O7 dichlorine heptaoxide

N2O4 dinitrogen tetraoxide

N2O dinitrogen oxide

Alkanes: page 71

How to predict the composition of

ionic compounds from names

The charges must be balanced!

Net charge is zero

Example: aluminum hydroxide


ionic compounds


Net charge is zero

Example: aluminum hydroxide

Aluminum is Al3+

Hydroxide is OH–

Al(OH)3

AlOH3 is incorrect

H O


ionic compounds


Net charge is zero

Example: iron (III) [ferric] oxide


ionic compounds


Net charge is zero

Example: iron (III) [ferric] oxide

Iron (III) is Fe3+

oxide is O2–

balance: Fe2O3

Fe2(O)3 is incorrect


ionic compounds


Net charge is zero

Example: zinc carbonate


ionic compounds


Net charge is zero

Example: zinc carbonate

Zinc is Zn2+

carbonate is CO32–

balance: ZnCO3

Zn(CO3), Zn(CO3)1 are incorrect

2-

carbonate


ionic compounds


Net charge is zero

Example: cesium carbonate

2-

carbonate


ionic compounds


Net charge is zero

Example: cesium carbonate

Cesium is Cs+

carbonate is CO32–

balance: Cs2CO3

Cs2(CO3), Cs2(CO3)1, (Cs)2CO3

are all incorrect

2-

carbonate

Molecular Weight (MW or FW)

molecular mass (weight) = sum of all atomic masses

Molecular Weight (Mass) is the same thing

as Formula Weight (Mass)

[ FW ]

NaCl

Molecular Mass of H2O is 2"1.008 + 16.00 = 18.02

Molecular Weight (MW)

What is the molecular weight of aluminum sulfate?



• Aluminum sulfate is Al2(SO4)3

• FW[SO4] = 32.07 + 4"16.00 =

• FW[Al2(SO4)3] = 2"26.98 + 3"96.07 =

96.07

342.17



• Aluminum sulfate is Al2(SO4)3

• Al2(SO4)3 = Al2S3O12

• FW[Al2(SO4)3] = 2"26.98 + 3"32.07 + 12"16.00 = 342.17


What is the molecular weight of copper (II) sulfate

pentahydrate?

• CuSO4•5H2O

• FW[CuSO4•5H2O] = 63.55 + 96.07 + 5"18.02 = 249.72

Mixtures

• heterogeneous

has boundaries between component (phase separation)

• homogeneous

no boundaries between component (phase separation)

solutions: liquid mixtures

aqueous solutions: the solvent is water

Mixtures: Separation

• filtration

• crystallization

• distillation

• extraction

• chromatography


• filtration (heterogeneous)

based on the difference in the state of matter (solid/liquid)


• crystallization (heterogeneous)

based on the difference in solubility


• distillation (homogeneous)

based on the difference

in volatility /boiling point


• extraction (homogeneous)

based on the difference

in solubility

(organic/aqueous)


• chromatography (homogeneous)

based on the difference in solubility (organic/aqueous)

and absorbance on immobile phase

Next Time: Stoichiometry

ionic compounds: formation - florida state universityzakarian/az_personal_web_cz/chm1050... · some...

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