Atoms, Molecules, and Ions

Chapter IIA Quick Survey

Fundamental Chemical Laws

These laws led to the discovery that all matter is composed of atoms

(1) Law of Conservation of Mass Frenchman Antoine Lavosier Matter can’t be created or

destroyed

Fundamental Chemical Laws cont… (2) Law of Definite Proportion (Constant

Composition) Frenchman Joseph Proust A compound always contains the same

percentage by mass of each element in it.

For example all samples of CO2 will always be 1 part C (12.01 g C) to 2 parts O (32 g O)

Fundamental Chemical Laws cont… (3) Law of Multiple Proportions Englishman John Dalton When two elements will form more

than one compound those two elements will always combine in whole-number ratios

For example: 1 gram of oxygen will combine with 1.750, 0.875, or 0.4375 grams of nitrogen

Dalton’s Atomic Theory Elements are made of tiny particles called

atoms All atoms of a given element are identical,

atoms of different elements are different Chemical compounds form when atoms of

different elements combine with one another

A chemical reaction merely involves the rearrangement of atoms, hence mass is conserved

Atomic Theory History The electron Discovered by J.J. Thomson during experiments

with cathode ray tubes Cathode Ray tube The same results were obtained regardless of

various metals being used as the electrodes. The same amount of deflection

Since all atoms are neutral he proposed there must be an equal amount of positive charge in atoms

But he did not discover the source of positive charge Plum-pudding model of the atom

Atomic Theory History cont…

The source of positive charge was discovered by Thomson’s student Ernest Rutherford.

Rutherford is best remembered for his Gold – Foil Experiment

Demonstration of the Experiment

Atomic Theory History cont… Millikan’s Oil Drop Experiment allowed for

the calculation of the charge of an individual electron

The Oil Drop Experiment By varying the voltage in the two plates

Millikan could determine the amount of charge needed to counterbalance the force of gravity. Using this information with the known charge to mass ratio of the electron, he could calculate the mass of an electron.

9.11 x 10-31 kg

The Modern View of Atomic Structure

The atom contains a tiny nucleus approximately 10-13 cm in diameter with electrons circling it at a distance of about 10-8 cm from the center

Protons and neutrons make up the nucleus and are held together by the strong nuclear force

The Modern View of Atomic Structure

Mass of subatomic particles Charge of subatomic particles While all atoms are composed of

the same components it is the arrangements of the electrons that give atoms their different chemical properties

The Modern View of Atomic Structure

Writing the symbol of the elements and counting the number of protons, neutrons, and electrons

The same atom with a different number of neutrons and hence mass are known as isotopes

Molecules and Ions Atoms are held together in compounds by chemical

bonds Chemical bonds fall into 2 major categories (there are

others, but for now we will focus on only these two) Covalent bonds – sharing of electrons between atoms

resulting in molecules Ionic bonds – resulting from a transfer of electrons from

one atom to another. The resulting ions formed are attracted to one another forming an individual unit cell (not a molecule)

The compounds formed from ionic bonds are known as salts

The periodic table

Review of organization Groups Periods Metals Nonmetals Metalloids

Nomenclature of inorganic compounds

Simple binary ionic compounds Type 1 – when the cation only forms

one charge Cations keep their names Anions have the end of their name

changed it ide Examples:

Nomenclature of inorganic compounds Simple binary ionic compounds

Type II – when the cation forms more than one charge

Cation must be identified by following it with a Roman numeral to represent the charge on the cation

Anion ending is still just change to ide Examples

Nomenclature of inorganic compounds

Ionic compounds that contain polyatomic ions The same rules for ionic compounds

already introduced still apply The polyatomic ions name is never

changed Examples

Nomenclature of inorganic compounds Covalent compounds Use prefixes Mono, di, tri, tetra, penta, hexa, hepta,

octa, nona, deca The first element only gets a prefix if

there is more than one The second element always gets a prefix Examples

Simple Organic Compounds Hydrocarbons

Nothing but carbon and hydrogen Methane, ethane, propane,

pentane, hexane, heptane, octane, nonane decane

Formula is CnH(2n + 2)

All of these fit into a category known as alkanes

Simple Organic Compounds Alkenes

Hydrocarbon with a double bond CnH2n

Examples Alkynes

Hydrocarbon with a triple bond CnH(2n – 2)

Examples

Hydrocarbon Derivatives Alcohols Hydrocarbons with one of the H’s of the

end removed and replaced with OH The OH is called a hydroxyl group and is not

to be confused with the hydroxide ion that has a 1- charge on it.

Same name just change the ending to ol Examples

Hydrocarbon Derivatives

Carboxyllic Acids Aldehydes Ketones Ethers Amines Esters

Naming Acids

Non- Oxygen Acids Give a prefix hydro and a suffix ic

followed by the word acid Examples

HCl, HCN, HBr, HI, HF

Oxyacids Contain a polyatomic ion If the polyatomic ion end in ate change

the ending to ic Examples H2SO4, H3PO4, HC2H3O2, HClO4

If the polyatomic ion ends in ite change the ending to ous Examples H2SO3, H3PO3, HNO2, HBrO2

Practice

68 – 71 p. 77 End of chapter 2