Elements and Compounds of

Chemistry

Naming and Formulas

The Periodic Table

The Periodic Table The most significant tool that chemists use

to organize and use chemical facts.

Properties of elements are organized into Groups: columns Periods: rows

Table Information Atomic number

Atomic symbol

Atomic weight (average)

Molecules Groups of atoms that are chemically

bonded Diatomic molecules: two atoms of the same

element H, N, F, O, I, Cl, Br (mnemonic device)

Molecular compounds: atoms to two or more different elements

Formulas Molecular formula: indicate the actual

numbers of atoms in a molecule Ex: C2H8

Empirical formula: give only the relative number of atoms of each type Ex: CH4

Structural Formula Molecular and empirical formulas do not

give any indication of how the atoms are linked or oriented to each other.

Structural formulas shows which are attached to which.

Ions Ions are electrically charged atoms

Cations: positively charged ions (Na+)

Anions: negatively charged ions (Cl-)

Polyatomic ions: atoms joined in a molecule that together carry a charge (OH-)

Predicting ionic charges Pattern: left side positively charged ions

Group 1: +1 Group 2:+ 2 Group 6: -2 Group 7: -1 Group 8: 0

Ionic Compounds Compounds composed of electrostatically

attracted cations and anions.

Typically made of metals (cations) and nonmetals (anions)

Molecular compounds are generally considered to be made of nonmetals.

Nomenclature There are more than 10 million known

chemical substances Chemists have created a standardized

system for naming compounds IUPAC Inorganic Organic

Names and Formulas of Ionic Compounds Naming cations (metals)

Rule: cations have the same name as the metal they came from

Some metals can form different charges, in this case add a roman numeral after the ion to represent the charge. Ex: Cu2+ (copper II ion)

Some cations are made from nonmetals and are polyatomic. Their names end in –ium

Ex: NH4+ (ammonium ion)

Naming Anions Rule: monatomic anions are named by

dropping the ending of the element and adding –ide Ex: H- hydride or F- flouride

Polyatomic ions that contain oxygen (oxyanions) have names that end in –ate or -ite

Naming ionic compounds Rule: names of ionic compounds are the

cation name followed by the anion name. Practice:

BaBr2

Al(NO3)3

FeCl3

Naming Binary Molecular Compounds Name the element farthest to the left on

the periodic table first If they are in the same group the lower

one is named first Change the ending of the second element

to –ide Greek prefixes are used to indicate the

number of atoms of each element present Mono is not used for the first element.

Practice IF5

XeO3

Dihydrogen monoxide Carbon tetrachloride Tetraphosphorus hexasulfide

The binary compounds of hydrogen are special cases. They were discovered before a convention was adopted and hence their original names have stayed.

Hydrogen forms binary compounds with almost all non-metals except the noble gases. Examples

HF - hydrogen fluorideHCl - hydrogen chloride H2S - hydrogen sulfide

Water H2O is not called dihydrogen monoxide

Binary compounds of Hydrogen

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When many hydrogen compounds are dissolve in water they take on the form of an acid. Special rules apply to acids. The “ite” suffix becomes “ous” and the “ate” suffix becomes “ic”

Acids

HCl Hydrochloric Acid Cl- Chloride

HNO2 Nitrous Acid NO2- Nitrite

HNO3 Nitric Acid NO3- Nitrate

H2SO3 Sulfurous Acid SO32- Sulfite

H2SO4 Sulfuric Acid SO42- Sulfate

H3PO3 Phosphorous Acid PO33- Phosphite

H3PO4 Phosphoric Acid PO43- Phosphate

H2CO3 Carbonic Acid CO32- Carbonate

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Chemical Reactions Elements and compounds frequently

undergo chemical reactions to form new substances

In a chemical reaction, chemical bonds are frequently broken and new chemical bonds are formed

Atoms are neither created nor destroyed in an ordinary chemical change

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Chemical Reactions A balanced chemical reaction is used to

describe the process that occurs in a chemical change.

For example: Zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen gas.

This chemical reaction could be written asZn + 2 HCl ZnCl2 + H2

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Reactants and Products In the chemical reaction

Zn + 2 HCl ZnCl2 + H2

Reactants Products

This shorthand way of describing a chemical reaction is known as a chemical equation

The starting materials are shown on the left and are known as reactants

The substances formed are shown on the right and are known as the products

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Balancing a Chemical Reaction A proper chemical reaction must be

balancedZn + 2 HCl ZnCl2 + H2

Reactants Products Each element must appear on both sides

of the arrow and equal number of times Chemical reactions can be balanced by

inserting numbers in front of formulas. These numbers are called coefficients

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Balancing Chemical Reactions Most simple equations can be balanced by

inspection Example: Balance the following equation

BaCl2 + K3PO4 Ba3 (PO4)2 + KCl

• There are 3 Ba on the right so we need coefficient of 3 in front of BaCl2

• There are 2 PO4 on the right so we need a coefficient of 2 in front of K3PO4.

• This leaves 6 K on the left so we need a coefficient of 6 in front of the KCl on the right

The balanced equation is

3 BaCl2 + 2 K3PO4 Ba3 (PO4)2 + 6 KCl

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Balancing Chemical Reactions An equation is balanced when there are the same

number and kind of atoms on both sides of the arrow

3 BaCl2 + 2 K3PO4 Ba3(PO4)2 + 6 KCl

Reactants (Left) Products (Right)

Ba 3 Ba 3

Cl 3 x 2 = 6 Cl 6

K 2 x 3 = 6 K 6

P 2 P 2

O 2 x 4 = 8 O 2 x 4 = 824

State Symbols State symbols are often added to chemical equations.

CaCO3 (s) + 2 HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l)

Symbols

(s) Solid

(l) Liquid

(g) Gas

(aq) Aqueous (Water Solution)

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Types of Reactions There are many kinds of chemical

reactions that occur. Some are very simple while others are very complex and may occur in multiple steps.

A number of reactions conform to some relatively simple patterns

Understanding and identifying these patterns can be helpful in predicting the products of similar reactions

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Direct Combination In a direct combination, two elements or

compounds combine to form a more complicated product

ExamplesCaO + CO2 CaCO3

2 H2 + O2 2 H2O

2 FeCl2 + Cl2 2 FeCl3 N2 + O2 2 NO

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Direct Combination In a direct combination, two elements or

compounds combine to form a more complicated product

ExamplesCaO + CO2 CaCO3

2 H2 + O2 2 H2O

2 FeCl2 + Cl2 2 FeCl3 N2 + O2 2 NO

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Single Replacement In a single replacement, one substance

(usually an element) takes the place of another in a compound

ExamplesZn + H2SO4 ZnSO4 + H2

Cl2 + 2 KBr 2 KCl + Br2

Mg + CuCl2 MgCl2 + Cu

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Double Replacement In a double replacement, two substances

exchange places in their respective compounds

ExamplesAgNO3 + NaCl AgCl + NaNO3

3 CaCl2 + 2 K3PO4 Ca3(PO4)2 + 6KCl BaCl2 + Na2SO4 BaSO4 + 2NaCl

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