The elements in Group 7 of the Periodic Table are called the halogens. They include chlorine, bromine and iodine. Learn about their properties and uses, then take a quiz.

The team at Periodicvideos has created a TED-Ed Lesson for every element of the periodic table. This one is about number 7 on the periodic table: nitrogen. It's the most abundant element in Earth's atmosphere. [4:03]

The team at Periodicvideos has created a TED-Ed Lesson for every element of the periodic table. This one is about phosphorus, an incredibly flammable element found in certain bombs and your body. [3:49]

The team at Periodicvideos has created a TED-Ed Lesson for every element of the periodic table. This one is about yttrium. It is found in moon rocks and bullet-proof glass. Come with us to Sweden to discover it.

The team at Periodicvideos has created a TED-Ed Lesson for every element of the periodic table. This one is about rubidium. Take this lesson to see it dropped in water! Yet another experiment in our "small metallic collider." [4:25]

The team at Periodicvideos has created a TED-Ed Lesson for every element of the periodic table. Here are five grams of caesium in water, but did you know caesium is also used to define the length of a second? [7:17]

On this site, investigate the alkali metals of the periodic table. Find out which elements are in this group, properties, similarities, and other facts.

Study the noble gases on this site. Learn about where to find them on the periodic table, what elements are in this group, and other facts.

Explore the halogens of the periodic table. Learn about which elements are in this group and the properties, similarities, and other facts.

This site provides a fact sheet with information on the basic data and properties of Indium. It also includes some of its uses.