Group 17 elements: Chemical properties

Group 17 elements, called halogens, are p block elements present at the second column to the right of the periodic table. The group 17 elements, consisting of highly reactive elements, are as follows- Fluorine(Fl), Chlorine(Cl), Bromine(Br), Iodine(I), Astatine(As), and Tennessine(Ts). Group 17 elements are non-metallic and extensively reactive. Out of the six elements, Astatine is a radioactive element. To arrive at the oxidation state of Group 17 elements, we should know the electronic configuration of the outermost shell of the elements. Group 17 elements exist as diatomic molecules and are found in all three states of matter (solid, liquid, and gas). Since the outermost shell of the halogens lacks one electron to reach its nearest noble gas configuration, they are extensively attractive to electrons of other metals and non-metals. The oxidation state of group 17 elements is -1.

The Group 17 elements on the periodic table

Group 17 elements consist of six elements. The Group 17 elements acquire the second right column of the periodic table. Since those elements are found on the periodic table’s p block, they are also referred to as p block elements. The outermost shell electronic configuration of the group 17 elements is ns2np5.

Occurrence of Group 17 elements

As halogens are highly reactive nonmetals, they never exist in their free state. Halogens react with other metals and non-metals to form halides and can exist in solid, liquid, and gaseous states. Fluorine and chlorine exist in the gaseous state at standard pressure and temperature. On the other hand, bromine exists as a liquid, and iodine exists as a solid. Astatine, a radioactive element, is found in the solid-state. Fluorine is found in the bones and teeth of organisms; they are found in plants and soil. Chlorine occurs in its natural state in the earth’s crust. It is also extensively found in seawater, while iodine is naturally found in ocean water. 

Group 17 elements: Chemical properties

The general properties of Group 17 elements: Chemical properties vary, but the physical properties remain the same in most cases. The chemical properties of group 17 elements can be categorised into aspects, such as their dissociation enthalpies, oxidising strength, reaction with metals, and reaction with hydrogen, oxygen, and water.

Dissociation enthalpies of group 17 elements

The elements of group 17 possess very low dissociation enthalpies, which results in their dissociation into atoms efficiently and reacting with other metals and non-metals to form halides. The bond dissociation enthalpies of group 17 elements can be expressed in the decreasing order as follows: 

Chlorine>Fluorine>Bromine>Iodine. It can be found that chlorine has the highest dissociation enthalpy while iodine has the lowest dissociation enthalpy. 

Oxidising strength of group 17 elements

As halogens are highly reactive, they are potent oxidising agents. The oxidising state of Group 17 elements declines as we move down the group. It can be said that Fluorine has the highest oxidising strength, while iodine has considerably low oxidising power. In order of their oxidising strength, halogens can be categorised as follows: 

Fluorine>Chlorine>Bromine>Iodine. 

Reducing the strength of group 17 elements

Halogens act as reducing agents. They have high reducing strengths on moving down the group; since the atomic sizes of the group 17 elements increase, their tendency to lose electrons increases. As a result, their reduced character increases. Thus, Fluorine has the lowest reducing strength, and iodine has the highest reducing strength. In terms of reducing strength, the group 17 elements can be categorised into order: 

Iodine>Bromine>Chlorine>Fluorine.

The reaction of group 17 elements with metals: 

It has been mentioned earlier that group 17 elements are highly reactive; halogens react with most metals vigorously to produce metal halides. Metal halides are binary molecules or compounds (salts), of which one part is the halogen atom, and the other part is the atom of the metallic element. In simple terms, metal halides are the compounds between metals and halogens. Metal halides are weak bases, while some act as Lewis acids. The reaction between Halogen and metal is highly exothermic. The reaction produces a bright light and an enormous amount of heat. Since metals are highly electro-positive and halogens are highly electro-negative, the product of their reaction, which is the metal halide, exists as an ionic substance. Some of the metal halides are covalent; as we move down the group, the ionic character of Group 17 elements decreases. In simple words, metal halides of Fluorine show the highest ionic character while the metal halides of iodine show the lowest ionic character. The order of their ionic nature can be written as follows: 

Fluorine>Chlorine>Bromine>Iodine.

The reaction of group 17 elements with hydrogen: 

Reactivity with hydrogen is one of the most vital chemical properties of the Group of 17 elements. Because of their reactive nature, halogens react with hydrogen to produce hydrogen halides. Hydrogen halides are acidic. The reaction of hydrogen with Halogen forms covalent bonds. Moving down the group, the reactivity of halogen increases, and bond strength between halogen and hydrogen decreases. Thus, Fluorine shows the highest tendency to react with hydrogen during low iodine tendency. Also, the acidic strength of hydrogen halides decreases on moving down the group. The decreasing order of the reactivity and acidic strength of Hydrogen halides can be written as HF>HCl>HBr>HI.

The reaction of Halogen with oxygen: 

In reaction with oxygen, halogens produce binary compounds. The produced binary compounds are unstable. The bonds between Halogen and oxygen are covalent. Oxides of halogens act as oxidising agents. In terms of reactivity, iodine is highly reactive to oxygen; on the other hand, bromine is comparatively less reactive to oxygen. 

Conclusion: 

Learning about the elements is one of the basics needed to know about chemistry. Thus, the group 17 elements (also known as Halogens) with the outer shell electronic configuration of ns2np5, their reactivity with gas and metals, chemical properties, and other general properties of them like reactivity, electronegativity, oxidising strength, reducing strength are learned in this article in detail. It would help the learners know about these elements and experiment with them in their higher studies. Hence, they have learned a big part of chemistry that they would use in their academics in the future.