An Introduction to Group 17 Elements
The Group 17 elements have an oxidation state of -1 when they combine with the left of their position and below elements of the periodic table. The elements of Group 17 of the periodic table are known as Halogens. Halogens are reactive nonmetals and include fluorine, chlorine, bromine, and iodine. The oxidation state of oxygen is usually -2 except in compounds with fluorine, oxygen has a positive oxidation number. All the elements of Group 17 form compounds in odd oxidation states (-1, +1, +3, +5, +7) but down the group importance of the higher oxidation states generally decreases. Group 17 elements only required one additional electron to form a full octet. This characteristic makes them more reactive than the other non-metal groups.
What are Halogens?
The Group 17 elements of the periodic table are known as Halogen, in greek: Halo means salt and genes mean producing, so collectively halogens means salt producing. They are highly reactive nonmetals. Fluorine, chlorine, bromine, iodine, and astatine are the elements. Halogens react with metals to form compounds called salt. The halogen elements have seven valence electrons, that's why they are located on the left of the noble gases on the periodic table. Halogens have seven electrons in their outermost shell (ns2np5) and one electron is short from the configuration of the nearest noble gas.
Oxidation State
1. All elements of the halogen family exhibit a -1 oxidation state.
2. Elements such as chlorine, bromine, and iodine also show +1, +3, +5, and +7 states.
3. When chlorine, bromine, and iodine, halogens in combination with small and highly electronegative atoms of fluorine and oxygen, the higher oxidation state is realized.
4. The oxoacids and oxides of bromine and chlorine have +6 and +4 states. Fluorine atoms can not expand their octet, because there are no valence shell d orbitals in fluorine.
5. Fluorine is the most electronegative element and exhibits only -1 oxidation state.
Physical Properties
Physical state: Fluorine and chlorine are gases on the other hand bromine is a liquid and iodine is a solid.
Colour: Group 17 elements have a variety of colours. For example, iodine is dark voilet in colour and Fluorine is pale yellow in colour.
Solubility: Chlorine and Fluorine are soluble in the water on the other hand Iodine and Bromine are less soluble in water.
Chemical Properties of Halogens
1. Being highly reactive, halogens react with metals and non-metals in order to form halides. As we move down the group reactivity of halogens decreases. Halogens have strong oxidizing properties among the halogen element, F2 is the strongest oxidizing halogen, it easily oxidizes the other halide ions present in the solid phase, or in the solution. Generally, halogen oxidizes the halide ions which are of higher atomic number. For Example:
\[F_{2} + 2X^{-} \rightarrow + X_{2}\] (where , X = cl, Br or l )
2. With the help of reaction of halogens with water, the relative oxidizing nature can be illustrated. Where chlorine and bromine react with water and form hydrohalic and hypohalous acid. In a non-spontaneous way, iodine reacts with water. With water in the acidic medium I- can be oxidized. For example:
\[4l^{-} (aq) + 4H^{+} (aq) + O_{2} (g) \rightarrow 2I_{2} (s) + 2H_{2} O (I)\]
General characteristics of Group 17 elements
1. Characteristics of Halogen Family
2. Electronic Configuration
The halogen family members have seven valence electrons, while halogens have seven electrons in their outermost orbit. From the nearest noble gas configuration halogens have one electron short. The configuration of the halogen family is given as ns2np5.
3. Electronegativity of Halogen Family
Fluorine: 4.0
Chlorine: 3.0
Bromine: 2.8
Iodine: 2.5
Astatine: 2.2
Explain Relative Reactivity
Among the halogen family, fluorine is considered to have the most reactivity. This is mainly because of the low dissociation energy it possesses when compared to other elements in the family. And with most of the other elements fluorine can create strong and stable bonds.
While meeting the elements in the halogen family. Both chlorine and fluorine are gases seen at room temperature. While bromine is a reddish-brown liquid with approximately 20 degrees Celsius. Under such temperature, iodine can create crystals of dark violet.
Do you know what electron affinity is? From a free atom or ion energy is released in the form of an ion. And that rate is called electron affinity. Almost all of the elements in the halogen family do have the same electron affinity. And they differ only slightly by their values. In the periodic table, halogens do have a higher electron affinity. A similar concept is what electronegativity is. It is the property of elements to attract electrons. And it is the highest for fluorine. In other words, we can say the urge of the element to become stable by completing the octet.
Fun Facts
Group 17 elements are called “halogens” because they give salts when they react with metals.
Group 17 elements are very reactive nonmetals. The electronic configuration of the valence shells of these electrons is ns2np5. Thus, in the outermost shell of these elements, the number of electrons is 7. These elements have various colours. Fluorine and chlorine are soluble in water, bromine and iodine are less soluble in water. Fluorine and chlorine are gases, on the other hand, bromine is liquid and iodine is solid.
In our day to day life, we use fluoride in water and also in toothpaste. It helps us to prevent tooth decay.
Bromine, on the other hand, has a bad odour and is also very strong. The name originates from the Greek word ‘bromos’ meaning stench.
FAQs on Oxidation State of Group 17 Elements
1. Mention some uses of group 17 elements?
The uses of Group 17 elements:
An important ingredient in toothpaste is Fluorine compounds. Because Fluorine compounds take care of teeth rotting by reacting with the enamel of the teeth.
Majorly chlorine is being used as a bleach and also used in the metallurgy of elements like platinum and gold.
Iodine is generally used as an antiseptic because it kills the germs on the skin.
2. Why are group 17 elements are dangerous?
All the Group 17 elements including fluorine, chlorine, bromine, iodine, and astatine are highly reactive nonmetals and are highly electronegative due to their highly effective nuclear charge. Halogens can gain an electron through reaction with other elements due to their high reactivity. To biological organisms in sufficient quantities, halogens can be harmful or lethal.
3. Why do group 17 elements are strong non-metals?
The group of halogens do have one electron in the valence shell. It makes them have the affinity for taking one more electron to complete the octet for stability. So while in chemical reactions they react differently from metals. And this makes them non-metallic. And in addition to that as they are placed on the right side of the periodic table, they are highly electronegative.
4. In what container chlorine trifluoride should be kept?
It is advised to keep chlorine trifluoride in something which is oxidising. So, therefore, we can use steel or aluminium tanks as containers. This will help in creating a fluoride layer inside the tank. So as a result, the content inside the container won’t react with the metal present in the container elements.
The method was developed by rocket scientists as a way for finding a way to save concentrated nitric acid. So for getting the fluoride coating what they added was HF to the nitric acid in the container vessel.
For more information about group 17 elements now students can check out the Vedantu app and website for study resources.
5. Why are halogens coloured?
The electronic transition happens between the n orbitals and sigma orbitals that are empty. And it is the energy gap between these orbitals just mentioned that decides the colour for the halogens. The molecules of halogen exist in their diatomic form.
The contemporary colour absorbed will be the observed colour. The contemporary colour for iodine molecules is yellowish-green. However, the observed colour is purple for iodine.
6. What makes halogens very reactive?
It is because of the high electron affinity nature of these elements. All the elements in the family contain 7 electrons in the valence shell. So to be stable, all these elements will try harder to get one electron to fill the valence shell towards the octet state. As a result of gaining electrons, they release energy. So that shows halogens are highly reactive.
7. Why are halogen molecules seen as diatomic molecules?
It is the electronic configuration responsible for the diatomic molecule nature for halogens. They cannot form more than one bond. Thus they can only combine with others to form a bond. By sharing one electron from the other atom, it attains stability and exists as a diatomic molecule.
