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Chemistry for Changing Times

12thEdition

Hill and Kolb

Chapter 3

Atomic Structure:

Images of the InvisibleJohn Singer

Jackson Community College, Jackson, MI 2010 Pearson Prentice Hall, Inc.

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Electricity and the Atom

Electrolyte: A compound that conducts

electricity when molten or dissolved in water.

Electrodes: Carbon rods of metallic strips thatcarry electrical current.

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E

Anode: A positive

electrode.

Cathode: A negativeelectrode.

Electrolysis

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Ions

Io n: An atom or group of atoms with a

charge.

Anion: A negative ion.

Cation: A positive ion.

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Cathode Ray Tubes

Mid-1800s: Crookes tube

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Thomson Experiment

1897, Joseph John Thomson:

Determined the charge:mass ratio of cathode

rays (discovered electrons).

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Goldsteins Experiment:

Positive Particles

1886, Goldstein:

Observed positive

rays using a

perforated cathode.

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Electron Charge1909, Robert Millikan:

Using the oil-drop experiment, Millikan

discovered the charge of an electron.

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X-Rays

1895, Wilhem

Roentgen:

Using a cathode ray

tube, Roentgen

discovered X-rays.

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Radioactivity1895, Antoine Becquerel:

Discovered radioactivity.

Marie Curieand husband

Pierrecharacterizedradioactivity.

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Three Types of Radioactivity

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Three Types of Radioactivity

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Rutherford Gold Foil Experiment

Using an apparatus similar to that shown below,Ernest Rutherford discovered the atomic

nucleus.

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Rutherford Gold Foil

Experiment

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Subatomic Particles

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Atomic Structure

Atomic number: The number of protons in a

nucleus.

Mass number:The sum of protons andneutrons in a nucleus.

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Isotopes

Isotopes have the same atomic number, but

have different mass numbers (same number of

protons, but different number of neutrons).

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Nuclear Symbol

Z

X

A

X= Element symbol

A= Atomic number

Z= Mass number

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Electron Arrangement:

The Bohr ModelFlame tests: Different elements give different colors to

a flame.

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Electron Arrangement:

The Bohr Model

Cont inuous spectra:

When light emitted

from a solid substance

is passed through aprism, it produces a

continuous spectrum

of colors.

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Electron Arrangement:

The Bohr ModelLine spectra:

When light from a

gaseous substance

is passed through aprism, it produces a

line spectrum.

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Electron Arrangement:

The Bohr ModelQuantum: A tiny unit of energy produced or

absorbed when an electron makes a transition

from one energy level to another.

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Electron Arrangement:

The Bohr ModelWhen electrons are in the lowest energy state,

they are said to be in the ground state.

When a flame or other source of energy isabsorbed by the electrons, they are promoted toa higher energy state (excited state).

When an electron in an excited state returns to alower energy state, it emits a photonof energy,which may be observed as light.

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Electron Arrangement

Energy states or levels are sometimes called

shel ls.

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Electron Arrangement:

The Quantum ModelThe Quantum modelof the atom is a

probability-based model. It is composed of

principle energy levels, sublevels, and orbitals.

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Electron Arrangement:

The Quantum ModelPrincip le energy levels (shells):Roughly

correlate to the distance that an electron is froman atoms nucleus.

Sublevels (subshel ls): Each principle energylevel (n) is divided into n sublevels.

Orbitals: Orbitals are a region in spacerepresenting a high probability of locating anelectron. Each sublevel has one or more orbital.

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Electron Arrangement:

The Quantum Model

El t A t

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Electron Arrangement:

The Quantum Model

El t A t

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Electron Arrangement:

The Quantum Model

Electron

conf igurat ions:

Allow us to represent

the arrangement ofthe electrons in an

atom.

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Electron Arrangement:

The Quantum Model

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Electron Arrangement:

The Quantum ModelThe order-of-filling chart:

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Electron Arrangement:

The Quantum Model

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Electron Configurations and the

Periodic TableThe periodic tableis considered by many to be

the most predictive tool in all of chemistry.

It is composed of vertical columns called groupsor families and horizontal rows called per iods.

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Electron Configurations and the

Periodic TableGroups (fam i l ies): Vertical columns in the

periodic table. Groups contain elements with

similar chemical properties.

Periods: Horizontal rows in the periodic table.

Elements in a period demonstrate a range of

properties from metallic (on the left) to

nonmetallic (on the right).

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Electron Configurations and the

Periodic TableValence electrons:

Valence electro nsare the electrons in theoutermost principle energy level of an atom.

These are the electrons that are gained, lost,or shared in a chemical reaction.

Elements in a group or family have the samenumber of valence electrons.

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Electron Configurations and the

Periodic TableSome groups in the periodic table have special

names:

Alkali Metals: Group 1A

Valence electron configuration: ns1

Alkaline Earth Metals: Group 2A

Valence electron configuration: ns2

Halogens: Group 7A

Valence electron configuration: ns2np5 Noble Gases: Group 8A

Valence electron configuration: ns2np6

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Electron Configurations and the

Periodic Table Metals, Nonmetals, and Metalloids:

Metals

Metallic luster, conduct heat and electricity,malleable, and ductile. Examples are sodium andcopper.

Nonmetals

Dull luster, nonconductors, and brittle.

Examples are sulfur and bromine. Metalloids

Demonstrate properties of both metals andnonmetals. Examples are silicon and arsenic.

C f

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Electron Configurations and the

Periodic Table