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Chapter 2

Atoms, Ions, and the Periodic Table

Shaun Williams, PhD

Dalton's Atomic Theory

Law of Conservation of Mass

Law of Conservation of Mass - Experiment

A series of photos showing a flask containing a bubbling reaction sealed with a balloon. During the reaction, the balloon inflates but the mass remains constant.

Law of Definite Proportions

Dalton's Atomic Theory

Atomic Force Microscope Image of a Gold Surface

An atomic force microscope image of a gold surface show bumps for each of the atoms.

Structure of the Atom

The Inner Structure of the Atom

A Graphic of the Atom

A graphical representation of the atom show the protons and neutrons in the nucleus at the center of the atom and the electron in the outer parts of the atoms.

The Discovery of Electrons

The Cathode Ray Tube

A cathode ray tube showing the cathode ray (beam of electrons) bending in the presence of oppositely changed metal plates.

The Nuclear Atom

A diagram of the gold foil experiments showing most alpha particles passing through the atoms but some reflecting off glod nuclei.

Subatomic Particles

Subatomic Particles - Continued

Oil Drop Experiment

A diagram of the oil drop apparatus used in measuring the mass of the electron.

Atomic Number and Mass Number


Isotopes, Hydrogen, Deuterium, and Tritium

A diagram of the nucleus of hydrogen (1 proton), deuterium (1 proton and 1 neutron), and tritium (1 proton and 2 neutrons).


What about different numbers of electrons?

A Diagram of Cations and Anions

A graphic showing magnesium losing 2 electrons to form its 2+ cation and nitrogen gaining 3 electrons to form its 3- anion.

Atomic Mass

What is the mass of an atom?

A Diagram of a Mass Spectrometer

A graphic showing a beam of ions passing through an evacuated tube between the poles of a strong magnetic. The magnetic causes the beam to bend. Light species bend more that heavy species.

Relative Atomic Mass

Relative Atomic Mass - Example

An unknown element (X) discovered on a planet in another galaxy was found to exist as two isotopes. Their atomic masses and percent abundances are listed in the following table. What is the relative atomic mass of the element?

Isotope Mass (amu) Natural Abundance (%)
\( \chem{{}^{22}X} \) 21.995 75.00
\( \chem{{}^{20}X} \) 19.996 25.00

The Periodic Table

Mendeleev's Table

One of the first Periodic Tables

A photo of one of the first versions of the Periodic Table published by Mendeleev.

The Modern Periodic Table

Periodic Table

The Periodic Table from the textbook.

Metals, Nonmetals, and Metalloids

Images of Various Metals, Nonmetals, and Metalloids

Images of various elements.

Main-Group Elements and Transition Metals

Periodic Table with the Main-Group Elements Colored

The Periodic Table from the textbook color coded.

Common Group Names

Common Group Names - Continued

Sodium in Water

A photo of sodium violently reacting in water.

Ions and the Periodic Table

Ions on the Periodic Table

A periodic table showing where the various ions exist.