Group 17 elements

Introduction

When we go through the group 17 periodic table, we come across six vital elements: the P-block elements. These elements are- Fluorine (Fl), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (As), and Tennessine (Ts). The Group 17 elements are called ‘Halogens’ because they produce salt in reaction with metals. The term ‘Halogen,’ which means ‘salt former,’ is derived from two Greek words ‘Halo’ meaning ‘salt’ and ‘Gen,’ meaning ‘formation.’ Halogens are highly reactive elements, and they don’t exist in the free state because of their reactive nature. They are found to exist as diatomic molecules. Since the halogens are P-block elements, they have differentiating electrons entering the P- orbital. The electrons of the Group 17 elements have a valence shell electronic configuration as ns2np5. Thus, it can be seen that the halogens have 7 electrons in their outermost shell. The deficiency of one electron in their outermost shell misses them out to reach the nearest noble gas configuration.

Position of Group 17 elements periodic table.

The Group 17 elements consist of 6 elements, occupying the second column from the right in the periodic table. The Group 17 elements come under the group VIIA in the periodic table. They are the p block elements. Group 17 elements are also called halogens. 

Characteristic properties of Group 17 elements.

Coming to the point about the properties of Group 17 elements, their properties can be categorized into three groups: the physical properties, chemical properties, and atomic properties.

Physical properties of Group 17 elements.

Looking into the physical properties of Group 17 elements, they vary from element to element. Their physical properties can be broadly into-

• Physics state: 

Fluorine and Chlorine exist in the gaseous state, Bromine in the liquid state, while Iodine, Astatine, and Tennessine are in the solid-state at room temperature. It is to be noted that Astatine is a radioactive element.

•   Solubility: 

Fluorine and Chlorine, as both the elements exist in the gaseous state at room temperature, are soluble in water. On the other hand, Bromine, Iodine, and Astatine are less soluble in water.

• Colour: 

The Group 17 elements exhibit a variety of colors. As we move down the group, the color of the elements gets darker. Fluorine is pale yellow, and Bromine has a reddish-brown color. Iodine is found to be in dark violet. On the other hand, Astatine is dark in color.

• Melting and boiling points:

On moving down the group, the melting and boiling point of the Group 17 elements increase. This is because the size of the atoms of Group 17 elements enlarges as we move down the group. Fluorine has the lowest melting as well as boiling points. On the other hand, Iodine has the highest melting and boiling points.

Chemical properties of Group 17 elements.

The chemical properties of Group 17 elements can be categorized into aspects such as Oxidizing strength, reaction with Oxygen and hydrogen, and metals.

• Oxidizing strength:

Halogens are potent oxidizing agents. The oxidizing strength of Group 17 elements decreases as we go down the group. In short, it can be said that Fluorine is the most potent oxidizing agent and Iodine is considerably a weaker oxidizing agent. Halogens also act as reducing agents. Their reducing capacity decreases as we move down the group in the periodic table.

• Reaction with Oxygen and Hydrogen:

Halogens are insanely reactive. They react with oxygen to form oxides. They also react with Hydrogen to release acidic Hydrogen halides. The acidity of the halogens reduces as we move down the group, i.e., from HF to HI.

• Reaction with metals:

Since the Group 17 elements are very reactive, they react with most metals vigorously to produce metal halides. The reaction between Halogen and metal is exothermic and produces a bright light and enormous heat during the reaction. The produced metal halides are found to be ionic. The metal halides formed are ionic due to the high electro-positivity of metal and high electro-negativity of Halogen. As we move down the group, the ionic character of Group 17 elements decreases.

Atomic properties.

The atomic properties of Group 17 elements consist of basic properties such as the atomic radii of the halogen atom, Ionisation and electron gain enthalpy, and electro- negativity.

• Atomic radii:

As we move down the group, the atomic radii of Group 17 elements increase due to the addition of an extra energy level. Fluorine has the smallest atomic radii, while Iodine has the largest.

• Electro-negativity:

Halogens are highly electro-negative. In another way, it can be said that halogens are exceedingly greedy for electrons. They tend to attract electrons nearer to them. On moving down the group, the electronegativity decreases, i.e., Fluorine is highly electro-negative while Iodine is less electro-negative.

• Ionization and electron gain enthalpy:

As we move down the group, the ionization enthalpy and the electron gain enthalpy of Halogen decreases (the electron gain enthalpy of Chlorine is higher than Fluorine which is an exception).

Uses of Halogens or Group 17 elements.

1. Fluorine is widely used in toothpaste. Compounds like Teflon are produced using Fluorine. It is also used in ceramics. It is a vital element in chlorofluorocarbons.
2. Chlorine is used to manufacture bleach, dyes, drugs, and other organic compounds. It is used for purifying drinking water, sterilizing hospitals and clinical equipment. It is widely used in manufacturing PVC. It is a significant constituent of pesticides like DDT.
3. Bromine is used in the preparation of dyes and medicines. Because of its fire-resistant properties, it is used in fire extinguishers. It is also used in certain pesticides.
4. Iodine is most widely used in preparing salt. It is used in disinfectants ( tincture Iodine), dyes, and inks. 

Conclusion

Group 17 elements, or halogens, are the vital elements of the periodic table. They have various chemical as well as physical properties. Though they are a group of reactive elements, they have significant uses in our day-to-day life. They have been used from treatment options to acting as disinfectants. The article covers all the characteristics associated.