Elements and Compounds of Chemistry Naming and Formulas

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: C 2 H 8  Empirical formula: give only the relative number of atoms of each type Ex: CH 4

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: Cu 2+ (copper II ion)  Some cations are made from nonmetals and are polyatomic. Their names end in –ium  Ex: NH 4 + (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: BaBr 2 Al(NO 3 ) 3 FeCl 3

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  IF 5  XeO 3  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 fluoride HCl - hydrogen chloride H 2 S - hydrogen sulfide Water H 2 O is not called dihydrogen monoxide Binary compounds of Hydrogen 17

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 HClHydrochloric Acid Cl-Chloride HNO 2 Nitrous AcidNO 2 - Nitrite HNO 3 Nitric AcidNO 3 - Nitrate H 2 SO 3 Sulfurous AcidSO 3 2- Sulfite H 2 SO 4 Sulfuric AcidSO 4 2- Sulfate H 3 PO 3 Phosphorous AcidPO 3 3- Phosphite H 3 PO 4 Phosphoric AcidPO 4 3- Phosphate H 2 CO 3 Carbonic AcidCO 3 2- Carbonate 18

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 19

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 as Zn + 2 HCl  ZnCl 2 + H 2 20

Reactants and Products  In the chemical reaction Zn + 2 HCl  ZnCl 2 + H 2 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 21

Balancing a Chemical Reaction  A proper chemical reaction must be balanced Zn + 2 HCl  ZnCl 2 + H 2 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 22

Balancing Chemical Reactions  Most simple equations can be balanced by inspection  Example: Balance the following equation BaCl 2 + K 3 PO 4  Ba 3 (PO 4 ) 2 + KCl There are 3 Ba on the right so we need coefficient of 3 in front of BaCl 2 There are 2 PO 4 on the right so we need a coefficient of 2 in front of K 3 PO 4. 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 BaCl K 3 PO 4  Ba 3 (PO 4 ) KCl 23

Balancing Chemical Reactions  An equation is balanced when there are the same number and kind of atoms on both sides of the arrow 3 BaCl K 3 PO 4  Ba 3 (PO 4 ) KCl Reactants (Left)Products (Right) Ba 3 Cl 3 x 2 = 6 Cl 6 K 2 x 3 = 6 K 6 P 2 O 2 x 4 = 8 24

State Symbols  State symbols are often added to chemical equations. CaCO 3 (s) + 2 HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l) Symbols (s) Solid (l) Liquid (g) Gas (aq) Aqueous (Water Solution) 25

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 26

Direct Combination  In a direct combination, two elements or compounds combine to form a more complicated product  Examples CaO + CO 2  CaCO 3 2 H 2 + O 2  2 H 2 O 2 FeCl 2 + Cl 2  2 FeCl 3 N 2 + O 2  2 NO 27

Direct Combination  In a direct combination, two elements or compounds combine to form a more complicated product  Examples CaO + CO 2  CaCO 3 2 H 2 + O 2  2 H 2 O 2 FeCl 2 + Cl 2  2 FeCl 3 N 2 + O 2  2 NO 28

Single Replacement  In a single replacement, one substance (usually an element) takes the place of another in a compound  Examples Zn + H 2 SO 4  ZnSO 4 + H 2 Cl KBr  2 KCl+ Br 2 Mg + CuCl 2  MgCl 2 + Cu 29

Double Replacement  In a double replacement, two substances exchange places in their respective compounds  Examples AgNO 3 + NaCl  AgCl + NaNO 3 3 CaCl K 3 PO 4  Ca 3 (PO 4 ) 2 + 6KCl BaCl 2 + Na 2 SO 4  BaSO 4 + 2NaCl 30