Name: halogens: trends and reactions
Uploaded: 2020-09-03T13:38:28.000Z
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Halogens

Halogens are a group of five nonmetallic elements &ndash; fluorine, chlorine, bromine, iodine, and astatine &ndash; belonging to Group 17. Elemental halogens exist as diatomic molecules.&nbsp;

At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Less is known about the properties of the fifth element, astatine, which is a rare and highly radioactive solid.&nbsp;

The physical properties of halogens, such as elemental color, vary moving down the group. Atomic radii increase&nbsp;with increasing atomic number, and the melting point and boiling point show an upward trend from fluorine to iodine. In contrast, periodic properties like electronegativity, reactivity, and electron affinity decrease down the group. &nbsp; &nbsp; &nbsp; &nbsp;

Electron configurations of halogens indicate that they have seven valence electrons and are one electron short of attaining their nearest noble gas configuration. Therefore, halogens exhibit high electronegativities with a strong tendency to gain one additional electron to complete their octet, making them highly reactive and powerful oxidizing agents compared to other groups.

Fluorine is the most potent oxidizing agent amongst halogens and iodine the least.

Halogens also exhibit highly negative electron affinities, which is the change in energy when an electron is gained by a neutral atom. It is expressed in kJ/mol, and the negative value indicates the exothermic nature of the reaction.&nbsp;

Halogens react with most metals to yield metal halides. For example, chlorine and sodium react to produce sodium chloride, which is an ionic compound.

Halogens react with hydrogen to form polar covalent compounds called hydrogen halides, which often dissolve in water to form hydrohalic acids.&nbsp;

Halogens also react with water. The reaction of fluorine with water is highly exothermic, producing hydrogen fluoride &mdash; a strong acid &mdash; and oxygen. Chlorine, however, reacts slower, producing hydrochloric acid and hypochlorous acid &mdash; a strong oxidizing agent.&nbsp;

Additionally, halogens can react with each other, producing binary, covalent compounds called interhalogen compounds. For instance, bromine reacts with fluorine forming bromine trifluoride. 
&nbsp;

halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. Astatine is a highly unstable radioactive element, so currently, most of its properties are unknown due to its short half-life. Tennessine is a synthetic element also predicted to be in this group.&nbsp;

The halogens are not found as single atoms but exist as diatomic molecules. The atomic radius increases from fluorine to iodine. The valence shell electron configuration of halogens is ns2np5, and they have a tendency to accept an electron to achieve the noble gas configuration. &nbsp;The various properties of halogens are listed in table 1.

Table 1: Properties of the Halogens.

<table style="margin-left: auto; margin-right: auto;">
	<tbody style="border: 1px solid black;">
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Element</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Electron Configuration</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Atomic Radius (pm)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">IE1 (kJ/mol)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">EA (kJ/mol)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Density at 25 &deg;C </td>
			<td style="color: black; border: 1px solid black; text-align: center;">Melting Point (&deg;C)</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">F</td>
			<td style="color: black; border: 1px solid black; text-align: center;">[He] 2s22p5</td>
			<td style="color: black; border: 1px solid black; text-align: center;">71</td>
			<td style="color: black; border: 1px solid black; text-align: center;">1680</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-328</td>
			<td style="color: black; border: 1px solid black; text-align: center;">1.70 g/L</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-219</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Cl</td>
			<td style="color: black; border: 1px solid black; text-align: center;">[Ne] 3s23p5</td>
			<td style="color: black; border: 1px solid black; text-align: center;">99</td>
			<td style="color: black; border: 1px solid black; text-align: center;">1250</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-348</td>
			<td style="color: black; border: 1px solid black; text-align: center;">3.12 g/L</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-101</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Br</td>
			<td style="color: black; border: 1px solid black; text-align: center;">[Ar] 4s24p5</td>
			<td style="color: black; border: 1px solid black; text-align: center;">114</td>
			<td style="color: black; border: 1px solid black; text-align: center;">1140</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-324</td>
			<td style="color: black; border: 1px solid black; text-align: center;">3.19 g/cm3</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-7</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">I</td>
			<td style="color: black; border: 1px solid black; text-align: center;">[Kr] 5s25p5</td>
			<td style="color: black; border: 1px solid black; text-align: center;">133</td>
			<td style="color: black; border: 1px solid black; text-align: center;">1010</td>
			<td style="color: black; border: 1px solid black; text-align: center;">-295</td>
			<td style="color: black; border: 1px solid black; text-align: center;">3.96 g/cm3</td>
			<td style="color: black; border: 1px solid black; text-align: center;">114</td>
		</tr>
	</tbody>
</table>

The electron affinities of halogens have large negative values; thus, the halogens are powerful oxidizing agents. Fluorine is the most powerful oxidizing agent of the group with the most negative electron affinity. The halogens react with metals to gain the electron and produce corresponding metal halide. For example, chlorine reacts with iron to give iron chloride and with sodium to give sodium chloride. The halogens react with hydrogen to form hydrogen halides, which dissolve in water to produce hydrohalic acids. Hydrofluoric acid is the weakest haloacid. Fluorine reacts vigorously with water. The reaction is highly exothermic and produces oxygen. The reaction of chlorine is less vigorous with water. The hypochlorous acid produced in this reaction is a strong oxidizing agent.

The halogens react with each other to form interhalogen compounds, many of which are binary compounds. The general molecular formula for interhalogen compounds is ABn, where A is the halogen with higher atomic number and is an odd number. Few examples of interhalogen compounds are ICl, IBr, BrF, BrCl, ClF. The halogens react with carbon to form commercially important compounds. &nbsp;For example, ethylene reacts with fluorine to give perfluoroethylene.

This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/6-5-periodic-variations-in-element-properties">Openstax, Chemistry 2e, Section 6.5: Periodic Variations in Element Properties.</a>

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

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halogens: trends and reactions

Halogens are Group 17 nonmetals that show clear trends in structure and reactivity. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is highly unstable and radioactive, so most of its properties are still unknown because it has a very short half-life. Tennessine is a synthetic element that is also predicted to belong to this group.

These elements do not usually exist as single atoms. Instead, they form diatomic molecules, which means each molecule has two atoms. Their atomic radius increases from fluorine to iodine, and their outer-shell electron pattern is ns2 np5. This electron arrangement helps explain why halogens tend to gain one electron and reach a noble gas configuration.

The table of halogen properties shows important changes across the group. Fluorine has the smallest atomic radius, while iodine has the largest. First ionization energy decreases from fluorine to iodine, and electron affinity stays strongly negative for the group. Because of this, halogens are powerful oxidizing agents, and fluorine is the strongest oxidizing agent in the group.

Halogens react with metals to form metal halides. For example, chlorine reacts with iron to make iron chloride, and it reacts with sodium to make sodium chloride. They also react with hydrogen to form hydrogen halides. When these dissolve in water, they produce hydrohalic acids, and hydrofluoric acid is the weakest haloacid.

Halogens also react with water, but not in the same way. Fluorine reacts very vigorously, and the reaction is highly exothermic, which means it releases a large amount of heat. It also produces oxygen. Chlorine reacts less vigorously with water, and the hypochlorous acid formed is a strong oxidizing agent.

Halogens can react with one another to form interhalogen compounds, which are often binary compounds. Their general formula is ABn, where A is the halogen with the higher atomic number and n is an odd number. Examples include ICl, IBr, BrF, BrCl, and ClF. Halogens also react with carbon to form useful compounds, such as perfluoroethylene from the reaction of ethylene with fluorine.

Halogens: Trends and Reactions

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Halogens are Group 17 nonmetals that show clear trends in structure and reactivity. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is highly unstable and radioactive, so most of its properties are still unknown because it has a very short half-life. Tennessine is a synthetic element that is also predicted to belong to this group. These elements do not usually exist as single atoms. Instead, they form diatomic molecules, which means...

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Explore halogen trends, from physical states and electron configuration to oxidizing strength, metal halides, hydrohalic acids, and interhalogen compounds.

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Halogens: Trends and Reactions

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