Why do halogens exist as diatomic molecules

Its oxidation state is always -1 except in its elemental, diatomic state in which its oxidation state is zero. Fluorine is extremely reactive and reacts directly with all elements except helium He , neon Ne and argon Ar.

In H 2 O solution, hydrofluoric acid HF is a weak acid. In addition, fluorine produces very powerful oxidants. For example, fluorine can react with the noble gas xenon and form the strong oxidizing agent Xenon Difluoride XeF 2.

There are many uses for fluorine, which will be discussed in Part VI of this article. Chlorine - Chlorine has the atomic number 17 and the chemical symbol Cl. Chlorine was discovered in by extracting it from hydrochloric acid. In its elemental state, it forms the diatomic molecule Cl 2. At room temperature it appears as a light green gas. Since the bond that forms between the two chlorine atoms is weak, the Cl 2 molecule is very reactive. Chlorine reacts with metals to produce salts called chlorides.

Chloride ions are the most abundant ions that dissolve in the ocean. Chlorine also has two isotopes: 35 Cl and 37 Cl.

Sodium chloride is the most prevalent compound of the chlorides. Bromine - Bromine has an atomic number of 35 with a symbol of Br. It was first discovered in In its elemental form, it is the diatomic molecule Br 2. At room temperature, bromine is a reddish- brown liquid. Bromine is more reactive than iodine, but not as reactive as chlorine. Also, bromine has two isotopes: 79 Br and 81 Br. Bromine consists of bromide salts, which have been found in the sea.

The world production of bromide has increased significantly over the years, due to its access and longer existence. Like all of the other halogens, bromine is an oxidizing agent, and is very toxic.

Iodine - Iodine has the atomic number 53 and symbol I. Iodine exists as a diatomic molecule, I 2 , in its elemental state. At room temperature, it appears as a violet solid. Iodine has one stable isotope: I.

It was first discovered in through the use of seaweed and sulfuric acid. Currently, iodide ions can be isolated in seawater. Although iodine is not very soluble in water, the solubility may increase if particular iodides are mixed in the solution.

Iodine has many important roles in life, including thyroid hormone production. This will be discussed in Part VI of the text. Astatine - Astatine is a radioactive element with an atomic number of 85 and symbol At. It is the only halogen that is not a diatomic molecule and it appears as a black, metallic solid at room temperature. Astatine is a very rare element, so there is not that much known about this element.

In addition, astatine has a very short radioactive half-life , no longer than a couple of hours. It was discovered in by synthesis. Also, it is thought that astatine is similar to iodine. However, these two elements are assumed to differ by their metallic character.

The periodic trends observed in the halogen group:. The melting and boiling points increase down the group because of the van der Waals forces. The size of the molecules increases down the group. This increase in size means an increase in the strength of the van der Waals forces. In addition, more energy levels are added with each period. This results in a larger orbital, and therefore a longer atomic radius.

If the outer valence electrons are not near the nucleus, it does not take as much energy to remove them. Therefore, the energy required to pull off the outermost electron is not as high for the elements at the bottom of the group since there are more energy levels.

Also, the high ionization energy makes the element appear non-metallic. The number of valence electrons in an atom increases down the group due to the increase in energy levels at progressively lower levels. The electrons are progressively further from the nucleus; therefore, the nucleus and the electrons are not as attracted to each other.

An increase in shielding is observed. An electron will not be as attracted to the nucleus, resulting in a low electron affinity. However, fluorine has a lower electron affinity than chlorine. This can be explained by the small size of fluorine, compared to chlorine. This is due to the fact that atomic radius increases in size with an increase of electronic energy levels. This lessens the attraction for valence electrons of other atoms, decreasing reactivity. This decrease also occurs because electronegativity decreases down a group; therefore, there is less electron "pulling.

A halide is formed when a halogen reacts with another, less electronegative element to form a binary compound. Hydrogen, for example, reacts with halogens to form halides of the form HX:. Hydrogen halides readily dissolve in water to form hydrohalic hydrofluoric , hydrochloric , hydrobromic , hydroiodic acids. The properties of these acids are given below:. It may seem counterintuitive to say that HF is the weakest hydrohalic acid because fluorine has the highest electronegativity.

Difluorine and dichlorine are room temperature gases. Dibromine is one of the few elemental liquids and the element is treated with a great deal of respect given its corrosiveness. And diiodine is a sublimable solid As the electronic cloud gets bigger as we go down the Group, "van der Waals" forces become more significant, and the elemental states reflect this.

Halogens in un combined state exist as diatomic molecules ,but they these discrete molecules have vander waal forces, why? May 23, Well, basically because these molecules have electrons Skip to main content. The Periodic Table. Search for:. Halogens Learning Objectives Name the halogens. Describe the physical properties of the halogens. Describe the chemical properties of the halogens.

How do you study a gas that does not exist as such in nature? Figure 1. Figure 2. The Great Salt Lake. Summary The halogens all have seven electrons in their outer shells. The electron configuration in the outer shell is ns 2 np 5. As the atomic number increases, the reactivity of the halogens decreases. Fluorine and chlorine exist as gases at room temperature, while bromine is a liquid, and iodine is a solid.

Why do we not know very much about astatine?