Halogens on the Periodic Table: Properties, Reactivity & Uses

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  • 0:01 Definition of Halogens
  • 0:31 Reactivity of Halogens
  • 1:27 Uses of Halogens
  • 2:30 Properties of Halogens
  • 3:02 Lesson Summary
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Lesson Transcript
Instructor: Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

Elements are grouped into families on the periodic table based on their chemical and physical properties. In this lesson, you will learn about a unique group known as the halogen family.

Definition of Halogens

Vertical columns on the periodic table containing elements that exhibit similar properties are commonly referred to by chemists as groups, or families. There are a total of 18 groups on the periodic table. The halogens are all elements that are found in group 17 of the periodic table. The halogens include fluorine, chlorine, bromine, iodine, and astatine. All of these elements are considered to be reactive nonmetals.

Reactivity of Halogens

Atoms of elements consist of a nucleus that contains protons and neutrons. The nucleus is surrounded by electrons that move around in orbits, or levels. Atoms of an element react with other atoms based on the number of electrons found in their outer orbit. These outer electrons are called valence electrons. For an atom of an element to be nonreactive, it must have eight electrons in its outer level. All members of the halogen family have seven valence electrons.

Because these atoms are so close to having a full set of eight valence electrons, they're very reactive. They show a chemical tendency to gain one electron by forming bonds and taking the electron from other atoms to attain a full set. Because of their chemical reactivity, these elements do not exist as single elements in nature. They are only found in compounds.

Uses of Halogens

Halogens have a variety of uses. Many household cleaning products contain halogen, such as the chlorine found in bleach. Fluorine and chlorine are both abundant in nature as compounds with other elements and are present in biological compounds. Table salt, used to flavor foods, is an essential part of the human diet. It is composed of sodium bonded with the halogen chlorine (NaCl). Humans also require iodine. The halogen iodine is found in iodized table salt as well.

Many towns and cities add fluorine to their water supplies. It is also found in toothpaste because it prevents tooth decay. Bromine is found in the compound silver bromide that is used in photographic film as a light-sensitive coating. Iodine is also used to sterilize the skin of a patient before surgery because it has antibacterial properties. Astatine is radioactive and is sometimes used as a radioactive tracer in cancer treatments.

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