This lesson explains what is represented by the atomic mass, and how it varies from one element to the next. Module includes a slideshow and a quiz.

Activity 1 in this module: What is the effect of changing the composition of an atom? Since all atoms contain protons, neutrons, and electrons, what makes one element different from another is examined.

Learn what atomic number is, and what happens if the numbers of protons in an atom changes.

At this site from the Purdue University, the elementary subatomic particles are described and electromagnetic radiation is detailed. Includes learning exercises and answers.

This lesson focuses on the structure of atoms. All substances are made from atoms. Each atom is made of a nucleus - containing protons and neutrons - surrounded by electrons. It provides a link to an assessment.

This lesson will explain that electrons are negatively charged particles with negligible mass and are found in pairs in orbitals surrounding the nucleus of an atom. It is 3 of 3 in the series titled "Subatomic Particles: The Electron."

This lesson will explain that neutrons are particles in the nucleus that have no charge and a mass of one amu. It is 2 of 3 in the series titled "Subatomic Particles: The Neutron."

The number of protons in the atom of an element determines its place in the Periodic Table. The number of electrons in an atom is the same as the number of protons. These electrons are arranged in shells or 'energy levels' around the...