Chemical Names and Formulas

6.1 Introduction to Chemical Bonding6.2 Representing Chemical Compounds6.3 Ionic Charges6.4 Ionic Compounds6.5 Molecular Compounds and Acids6.6 Naming and Formula Writing

6.1 Objectives Distinguish between ionic and molecular

compounds Define cation and anion, relate them to metal

and non-metal

metal/cation nonMetal/anion

6.1 Vocabulary Molecule Molecular compound Ions Cations Anions Ionic compounds

Introduction to Chemical Bonding

Molecules and Molecular Compounds Tend to have low boiling and melting points May be gases or liquids at room temperature (RT) Are composed of non-metals, CO2

Ions and Ionic Compounds, (+) and (-) Have balanced charges, 2(+) must have 2(-) Have high boiling and melting points, (solid at RT) Are composed of metals and non-metals

(combined)

Ions: Symbols and Names

Cations: these are metals that lose electrons When you lose a (-) you become more positive If Potassium (K) loses 1 electron it becomes K+1

Example: (19+ and 19–) changes to (19+ and 18-) Anions: these are nonMetals that gain electrons

When you gain a (-) you become more negative If Bromine (Br) gains one electron it becomes Br-1

Example: (35+ and 35-) changes to (35+ and 36-) Anions change their suffix to –ide, (Bromine to

Bromide)

Characteristics of CompoundsCharacteristic Molecular

CompoundIonic Compound

Representative Unit Molecule Formula Unit

Type of Elements nonMetals Metal and nonMetal

Physical State Solid, liquid , or Gas Solid

Melting Point Low, (below 300 C) High, (above 300C)

Questions What is the symbol and name for an Oxygen

atom that has gained two electrons? O2- and Oxide What is the symbol and name for an Iron atom

that has lost two electrons? Fe2+ and Iron (II)

Definitions A Molecule is the smallest electrically neutral

unit of a substance A Molecular compound are combinations of

atoms Ions are charged atoms or molecules Cations are positively charged (+) Anions are negatively charged (-) Ionic compounds combine the (+) and (-)

6.2 Objectives Distinguish among chemical formulas,

molecular formulas, and formula units Use experimental data to show that a

compound obeys the law of definite proportions

Vocabulary Chemical formula Molecular formula Formula unit Law of Definite Proportions Law of Multiple Proportions

Formula Unit is a crystal

HONClBrIF

Diatomic Molecules, (exist as two bonded atoms) (H) Hydrogen as H2

(O) Oxygen as O2

(N) Nitrogen as N2

(Cl) Chlorine as Cl2

(Br) Bromine as Br2

(I) Iodine as I2

(F) Fluorine as F2

Counting Atoms and Assigning Mass When elements react to form

compounds, they react in defined, whole-number ratios. The experiments that Dalton and others performed showed that reactions are not random events; they proceed according to precise and well-defined formulas.

Water, for example, is always made up of two parts hydrogen and one part oxygen. The chemical formula of a compound is written by listing the symbols of the elements together, without any spaces between them. If a molecule contains more than one atom of an element, a number is subscripted after the symbol to show the number of atoms of that element in the molecule. Thus the formula for water is H2O, never HO or H2O2.

Questions How are the images different? In every sample of Carbon Monoxide the mass

ratio is 3:4 for the mass of Carbon : Oxygen. In sample 1: Carbon is 9 grams and Oxygen is ____ In sample 2: Carbon is _____and Oxygen is 8 grams

Definitions

A Chemical formula shows the kind and number of atoms in a representative unit

A Molecular formula shows the kind and number of atoms in a molecule

A Formula unit is the lowest whole number ratio in a compound, when ions come together to form a crystal

Law of Definite Proportions: the masses of the elements in a compound always conform to a ratio

Law of Multiple Proportions: different compounds may have different ratios of the same elements

6.3 Objectives Use the Periodic Table to determine the

charge of an ion Define a polyatomic ion Name the most common examples of

polyatomic ions

Vocabulary Monoatomic ions Polyatomic ions

The Mono-Atomic Ions

See the table on page 143 for the Representative Elements

See the table on page 144 for some Transition Metal Elements

Some Transition Metal Ions

Complexes may be quite colorful The paint industry uses transition metal ions

to provide color

Poly-Atomic Ions

Ammonium ion is positive (+) Nitrate ion is negative (-) In each case there are multiple atoms acting

as a tightly bound unit The table on page 147 provides a good list

Questions

What is the charge on a Potassium atom that has changed to an ion?

What is the charge of a Bromine atom that has changed to an ion?

Using page 147, what is the charge of Sulfite? What is the charge of Iron (III)?

How would you write an ion of Cobalt (II)? What is the name of Sn+4 ?

Definitions Monoatomic ions are ions consisting of only

one atom Cation: Li+1

Anion: Br-1

Polyatomic ions are tightly bound groups of atoms that behave as a unit and carry a charge Cation: NH4

+1

Anion: Cr2O7-2

6.4 Objectives Apply the rules for naming and writing

formulas for binary compounds Apply the rules for naming and writing the

formulas for ternary ionic compounds

Vocabulary Binary compounds Ternary compounds

How to write a chemical formula

Start by identifying the types of atoms Hydrogen and Oxygen

Count the atoms of each type Two H and One O leads to the formula H2O

Naming a binary ionic compound

Determine the positive ion, in this case Sodium+

Determine the negative ion, in this case Chlorine-

Determine the charges (+) and (-), both are 1 The positive (cation) is first, then the anion Sodium Chloride is NaCl and has no charge

Naming a ternary ionic compound

Notice the green ball, (Mg+2), and the ball that is red/white, (OH-), the ratio is 1:2 or Mg(OH)2

Magnesium Hydroxide

Definitions Binary compounds are composed of two

elements NaCl

Ternary compounds are composed of three different elements CaCO3

6.5 Objectives Apply the rules for naming and writing

formulas for binary molecular compounds Name and write formulas for common acids

Binary molecular compounds

Prefixes for naming binary molecular:mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa-8 nona- 9

deca- 10 - diNitrogen tetraHydride, (N2H4)

Naming common acids

(aq) means it is in water Acids break apart in water Six acids are commonly

used, (see the chart at left) There are rules for naming

acids, (hydro- and –ic acids)

6.6 Objectives Use the flowchart in Fig. 6.21 to write the

name of a compound when given its chemical formula

Use the flowchart in Fig. 6.23 to write a chemical formula of a compound when given its name