Introduction to Halogens
Group 17 elements of the periodic table comprises Halogens. They come under the p-block elements of the modern periodic table. There are five Halogens and in order of valency in the periodic table they are as follows: Chlorine, Fluorine, Iodine, Bromine and Astatine. The word “Halogen” is a Greek word which means salt producer due to the properties of elements like Bromine, Chlorine and Iodine. Halogens exhibit high electronegativity and the anions formed become the anionic part of the salts which are widely found in seawater. Electronegativity is defined as the ability of an atom to accept an electron and form an octet. The last element of the group, Astatine, is radioactive in nature. In this article, students will learn about Halogens and their properties.
What are Halogens?
Halogens are highly reactive nonmetals belonging to the 17th group of the periodic table. They have seven electrons in their outermost shell with the electronic configuration ns2np5. They are highly electronegative in nature as they are only one electron short of the nearest noble gas configuration. Out of the five Halogens, Astatine is the only radioactive element. The Physical and Chemical properties of Halogens are greatly similar which is not observed in other groups.
Properties of Halogens
Physical Properties
Halogens exhibit smooth transitions in their Physical state. Chlorine and fluorine are glasses naturally, bromine is liquid in its natural state and iodine is solid in nature.
With change in atomic number, the melting and the boiling points of the elements change.
Halogens are usually coloured due to the absorption of radiation in their visible regions. Fluorine exhibits yellow color, bromine shows red color, Chlorine is greenish-yellow in color and iodine is violet.
Chlorine and fluorine dissolve in water completely, iodine and bromine are partially soluble in water but completely soluble in organic solvents such as chloroform disulphide.
Chemical Properties
Halogens show a -1 oxidation state, however, bromine, Chlorine and fluorine can also exhibit +1, +3, +5 and +7 oxidation states as well. The higher oxidation states are exhibited only when Halogens combine with highly electronegative atoms like oxygen and fluorine. They are usually highly reactive and can react with metals and nonmetals alike, thus, forming halides. They can readily accept an electron to complete electronic configuration and form an octet. Out of all the Halogens, fluorine is the strongest Oxidizing agent.
Trends Among Halogens
Reactivity of Halogens decreases down the group.
Halogens have a small atomic size.
They have a high nuclear charge.
Group 17 Trends Properties
The modern periodic table's group 17 consists of the following elements.
Chlorine
Fluorine
Iodine
Bromine
Astatine
These elements are called halogens. Halogen is a Greek word, which means a salt producer. These elements are known as salt producers due to the properties exhibited by bromine, chlorine, and iodine. They are highly electronegative in nature and form anions, which constitute the anionic part of salts found in the seawater. Astatine is the last element of the group and is radioactive in nature. These elements belong to the p block of the modern periodic table. The halogen family constitutes the most homogenous group after the alkali group in the modern periodic table.
Did You know?
Why is the electron affinity of chlorine more than that of fluorine?
Answer: This is due to the compact structure of fluorine. Chlorine has a larger atomic size hence it can accommodate more electrons, whereas the electrons in fluorine are closely-spaced. So, the crowded electrons in fluorine screen its effective nuclear charge, and thus, it exhibits a lower electron affinity.
FAQs on Halogens - Trends in Chemical and Physical Properties
1. What are halogens?
Elements of Group 17 of the periodic table are highly electronegative nonmetals known as Halogens. There are five Halogens- Chlorine, fluorine, bromine, iodine and astatine out of which Astatine is radioactive in nature and chlorine shows the highest electronegativity.
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2. Why do halogens exhibit colour?
Halogens absorb the colour of the visible range in different regions which causes valence electrons to get excited and jump to higher energy states. Thus, fluorine shows yellow colour, bromine shows red colour, Chlorine is observed to be greenish-yellow in colour and iodine exhibits violet colour.
3. Which is the strongest oxidizing agent in nature?
Fluorine is the strongest Oxidizing agent as it can readily accept an electron to form an octet, and oxidizes other elements to form halides. An element's reactivity and chemical properties are determined by the oxidation state exhibited by it.
4. Why chlorine has a higher electron affinity than fluorine?
Fluorine has a very small size, therefore, it is compact. So the crowded electrons in fluorine have a screening effect which can cause hindrance in electron acceptance. But Chlorine is relatively bigger than fluorine, so it can accommodate an electron very easily. Therefore, Chlorine shows a higher electron affinity than fluorine.
5. What are Pseudo Halogens?
Pseudo Halogens are usually compounds that have an oxidation state of -1. These compounds are usually formed by combining two or more p-block elements and have a negative charge. They are covalent compounds and complexes but can polymerize, unlike Halogens. The cyanide group with CN- is an example of a Pseudo Halogen.
6. Explain why halogens are more reactive?
Halogens require to gain only 1 electron to attain the octet of a noble gas configuration. Also, they are the smaller atoms in a period, so they have a high electronegativity (attraction for electrons), and tend to attract electrons in a bond. Hence, they can readily form a bond with any other metal or electropositive ion. In a covalent bond, halogens tend to attract shared pairs of electron
7. Why is a halogen called so?
The group 17 members in a periodic table are called halogens. Halogen is a Greek word, which means a salt producer. These elements are so-called because they are salt-forming compounds.
8. Why is fluorine coloured?
Halogens are much likely to absorb the radiation in the visible region. Then, they excite electrons to higher energy levels. Therefore, being the smallest with the maximum effective nuclear charge, fluorine will absorb high energy violet light and appears to be pale yellow. Thereby, the halogens are colored.