Atoms, Molecules, and Ions

Chapter 2The Atomic Theory (2.1)The Structure of the Atom (2.2)Atomic Number, Mass Number, and Isotopes (2.3)The Periodic Table (2.4)Molecules and Ions (2.5)Chemical Formulas (2.6)Naming Compounds (2.7)Introduction to Organic Compounds (2.8)

2.1 The Atomic Theory

What are the four hypotheses of Dalton’s Atomic Theory?

Figure 2.1, p. 30

2.1 The Atomic Theory

Law of Multiple Proportions:

If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers.

Example:

Nitrogen and oxygen combine to form 2 different compounds

Compound 1:10.00 g of oxygen combine to form 18.75 g of the compound

Compound 2:10.00 g of oxygen combine to form 14.38 g of the compound

What is the mass ratio of nitrogen between compound 1 and compound 2?

Figure 2.2, p. 31

Key Definitions

Law of conservation of massAtomElementCompound

Discovery of the Electron (J.J.Thomson, 1898-1903)Thomson experimented using cathode-ray tubes: ◦ high voltage was applied to the tube◦ ray was emitted by the negatively charged electrode

The ray was repelled by the negative pole of an applied electric field and also deflected by a magnetic field.

The beam consists of negatively charged particles, electrons.

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Figure 2.3, p. 32

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Figure 2.4, p. 32

Discovery of the Electron (Millikan, 1908)Measured charge of the electron:

by observing the rate of the fall of charged and uncharged oil droplets

Used the determined charge to calculate the mass of the electron

1923 Nobel Prize in Physics

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Plum Pudding Model

Figure 2.6 p. 34

(Uranium compound)

α-rays (positive charge)β-rays (negative charge)γ-rays (high energy-no charge)

charged metal plates

Figure 2.5 p. 33

Discovery of the Nucleus (E. Rutherford, 1910)Rutherford used a very thin gold foil and alpha particlesThe alpha particles went through the gold foil largely undeflected.A small number were slightly deflected and some of those were deflected back at the source.

Positive charge of the atom is concentrated in the nucleus – protons have an opposite charge of electrons and a mass of approximately 1800x an electron

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Experiments Leading to the Discovery of the Subatomic Particles

2.2 The Structure of the Atom

Figure 2.7, p. 34

atomic radius ~ 100 pm = 1 x 10-10 m

nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m

Rutherford’s Model of the Atom

“If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.”

electrons

Figure 2.8, p. 35

Key Definitions

ElectronProtonNeutron

Give relative mass, charge and location of each subatomic particle

Table 2.1, p. 36

2.3 Atomic Number, Mass Number, and Isotopes

True/False: An atom is neutral

True/False: The nucleus is always positively charged

Define atomic number (Z)Define atomic mass (A)Define isotope

The Isotopes of Hydrogen

Margin figure, p. 37

2.3 Atomic Number, Mass Number, and Isotopes

True/False: An atom is neutral

True/False: The nucleus is always positively charged

Define atomic number (Z)Define atomic mass (A)Define ion, cation, anion

2.4 The Periodic Table

Figure 2.9, p. 38

Key DefinitionsGroupPeriodNonmetal◦ Halogen◦ Noble gasesMetal◦ Alkali metal◦ Alkaline earth metal◦ Transition metal◦ Inner transition metal

Period

Group

Alkali M

etal

Noble G

as

Halogen

Alkali E

arth Metal

Figure 2.9, p. 38

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Hydrogen and water molecules are shown in the figure. What are the classifications of these substances?

A. Both are elements.B. Both are compounds.C. Hydrogen is a compound and water is an element.D. Hydrogen is an element and water is a compound.C

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Which nucleus is shown in the figure? A. 3He B. 2HeC. 3H D. 2H

What is the nuclear charge for palladium-104?A. +46 B. +58 C. +60 D. +104

How many electrons are in Al3+?A. 3 B. 10 C. 13 D. 16Cha

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2.5 Molecules and Ions

Key Definitions:◦ Molecule

Diatomic moleculePolyatomic molecule

◦ Molecular compounds◦ Molecular elements

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2.5 Molecules and Ions

Key Definitions:◦ Ion

Monoatomic ionPolyatomic ion

◦ Cation◦ Anion

S

OO

O

O 2-

Monoatomic Ions

Figure 2.10, p. 40

Table 2.3, p. 46

2.6 Chemical Formulas

Key Definitions:◦ Molecular formula◦ Empirical formula

2.6 Chemical Formulas

Figure 2.11, p. 41

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2.6 Chemical Formulas

Formula of ionic compounds◦ How do ionic compounds exist?◦ How do we write a formula for an ionic

compound (is it a molecular or empirical formula)?

Figure 2.12, p. 43

Table 2.3, p. 46

Practice (Moodle)

Which are ionic compounds?

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2.7 Naming Compounds

Ionic compounds◦ Transition metal compounds◦ Zinc, silver, cadmium, lead, tin◦ Polyatomic ions

Table 2.3, p. 46

2.7 Naming Compounds

Ionic compounds◦ Transition metal compounds◦ Zinc, silver, cadmium, lead, tin◦ Polyatomic ions

Molecular compounds◦ Compounds containing hydrogen◦ Common names

Table 2.4, p. 48

Figure 2.13, p. 49

2.7 Naming CompoundsIonic compounds◦ Transition metal compounds◦ Zinc, silver, cadmium, lead, tin◦ Polyatomic ionsMolecular compounds◦ Compounds containing hydrogen◦ Common namesAcids◦ Binary◦ OxoacidsHydrates

Figure 2.14, p. 51

Tables 2.5 and 2.6, p. 50-51

Which group on the periodic table contains the greatest number of molecular elements?

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What is this figure attempting to show?

What makes this figure confusing?

How does that relate to scale?

Margin Figure, p. 50