Group 7: Halogens

The Group 7 elements, also known as halogens, have seven electrons in their outer shell. They are non-metals that are reactive and are always found in combination with other elements. The halogens can be located in the second-to-last column of the periodic table.

Examples of halogens include:

  • Fluorine (F)
  • Chlorine (Cl)
  • Bromine (Br)
  • Iodine (I)

Halogens are diatomic elements, which means that they form molecules composed of two atoms that are covalently bonded together. For example, two fluorine atoms bond to form a fluorine molecule (F2).

A fluorine molecule is formed by the combination of two fluorine atoms. The atoms are represented as small spheres, each with seven electrons in its outer shell.

Below you can see the diatomic molecules of the other halogens.

Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2) are each represented as two joined spheres, with their atomic symbols indicated below.

Properties of the Halogens

HalogenState and appearance at room temperature
FluorineYellow gas
ChlorinePale green gas
BromineReddish brown liquid
IodineBlack solid

As you can see, halogens get darker as you move down the group.

Melting and boiling points

Halogens have distinct physical properties that vary as you move down the group. One of these properties is the melting and boiling points, which increase as you go down the group due to the increase in intermolecular forces.

The size of halogen molecules increases as you move down the group, causing the intermolecular forces to become stronger. This means that more energy is required to overcome these forces, leading to higher melting and boiling points.

A horizontal bar graph containing the different boiling and melting points of each element in group 7.

As you move down group 7, the halogens transition from gaseous to solid states due to increasing melting and boiling points.