This is a list of the radioactive elements of the periodic table. While all elements have some radioactive isotopes, these 37 elements have no stable isotopes. These elements are considered the "radioactive elements".

# Todd Helmenstine

Chemistry departments often have kits of plastic balls to stick together to represent atoms and their arrangement in molecules. These kits come with several different colors to easily distinguish one element from another. The choice of color for each atom is not arbitrary. The color code of these atoms is known as CPK colors.

## Molecule Atom Colors – CPK Colors

The ice to steam problem is a classic heat energy homework problem. This will outline the steps necessary to complete this problem and follow up with a worked example problem.

## Ice to Steam Problem – Heat Change Example Problem

These two heat of vaporization example problems will show how to use heat of vaporization to find the energy needed to change between liquid and gas phases.

## Heat of Vaporization Example Problem

This worked example problem will show how to use the period and length of a pendulum to calculate the acceleration due to gravity.

## How to Calculate Acceleration Due to Gravity Using a Pendulum

School is in session. This periodic table wallpaper looks like a teacher with exceptionally neat handwriting drew a periodic table on the chalkboard.

## Chalkboard Periodic Table Wallpaper

This example problem will show how to use the simple pendulum formula to find the length of a pendulum for a known period.

## Simple Pendulum Example Problem – Find the Length of a ...

A short example problem showing how to calculate the period of a simple pendulum.

## How to Find the Period of a Simple Pendulum – ...

Law of Cosines example problems showing how to derive the law and how to use it to find the lengths of the sides or angles of a triangle.