Halogens

The halogens are five non-metallic elements found in group 17 of the periodic table. The term “halogen” means “salt-former” and compounds containing halogens are called “salts”. All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. The halogens exist, at room temperature, in all three states of matter. When you look at our descriptions of the elements fluorine and chlorine you will see that they both have seven electrons in their outer shell. That seven-electron trait applies to all of the halogens. They are all just one electron shy of having full shells. Because they are so close to being happy, they have the trait of combining with many different elements. They are very reactive. You will often find them bonding with metals and elements from Group One of the periodic table. The elements in the column on the left each have one electron that they like to donate. They all form acids when combined with hydrogen. They are all fairly toxic. They readily combine with metals to form salts. They have seven valence electrons in their outer shell. They are highly reactive and electronegative. They all exist as diatomic molecules (two atoms) when in their pure form.

The Halogens are:

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

Fluorine (F)

Name: Fluorine
Symbol: F
Atomic Number: 9
Atomic Mass: 18.998404 amu
Melting Point: -219.62 °C
Boiling Point: -188.14 °C
Number of Protons/Electrons: 9
Number of Neutrons: 10
Classification: Halogen
Crystal Structure: Cubic
Density @ 293 K: 1.696 g/cm3
Color: Greenish

Chlorine (Cl)

Name: Chlorine
Symbol: Cl
Atomic Number: 17
Atomic Mass: 35.4527 amu
Melting Point: -100.98 °C
Boiling Point: -34.6 °C
Number of Protons/Electrons: 17
Number of Neutrons: 18
Classification: Halogen
Crystal Structure: Orthorhombic
Density @ 293 K: 3.214 g/cm3
Color: green

Bromine (Br)

Name: Bromine
Symbol: Br
Atomic Number: 35
Atomic Mass: 79.904 amu
Melting Point: -7.2 °C
Boiling Point: 58.78 °C
Number of Protons/Electrons: 35
Number of Neutrons: 45
Classification: Halogen
Crystal Structure: Orthorhombic
Density @ 293 K: 3.119 g/cm3
Color: Red

Iodine (I)

Name: Iodine
Symbol: I
Atomic Number: 53
Atomic Mass: 126.90447 amu
Melting Point: 113.5 °C
Boiling Point: 184.0 °C
Number of Protons/Electrons: 53
Number of Neutrons: 74
Classification: Halogen
Crystal Structure: Orthorhombic
Density @ 293 K: 4.93 g/cm3
Color: blackish