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

Gli alogeni sono un gruppo di cinque elementi non metallici fluoro, cloro, bromo, iodio e astato appartenenti al Gruppo 17. Gli alogeni elementari esistono come molecole biatomiche. A temperatura ambiente, il fluoro e il cloro sono gas, il bromo è un liquido e lo iodio è un solido.

Si sa molto meno circa le proprietà del quinto elemento, l'astato, che è un solido raro e altamente radioattivo. Le proprietà fisiche degli alogeni, come il colore elementare, variano spostandosi lungo il gruppo. I raggi atomici aumentano con l'aumentare del numero atomico, e il punto di fusione e il punto di ebollizione mostrano una tendenza al rialzo dal fluoro allo iodio.

Al contrario, proprietà come l'elettronegatività, la reattività e l'affinità degli elettroni diminuiscono nel gruppo. Le configurazioni degli elettroni per gli alogeni indicano che hanno sette elettroni di valenza e che possiedono un elettrone in meno per raggiungere le configurazioni dei gas nobili più vicini. Pertanto, gli alogeni mostrano elevate elettronegatività, con una forte tendenza a guadagnare un elettrone aggiuntivo per completare il loro ottetto, rendendoli agenti ossidanti altamente reattivi e potenti rispetto ad altri gruppi.

Il fluoro è l'agente ossidante più potente fra gli alogeni e lo iodio il meno potente. Gli alogeni mostrano affinità per gli elettroni altamente negative, dimostrate dal cambiamento di energia di un elettrone quando viene acquisito da un atomo neutro. È espresso in kilojoule per mole, e il valore negativo indica la natura esotermica della reazione.

Gli alogeni reagiscono con la maggior parte dei metalli per produrre alogenuri metallici. Per esempio, il cloro e il sodio reagiscono per produrre cloruro di sodio, che è un composto ionico. Gli alogeni reagiscono con l'idrogeno per formare composti covalenti polari detti alogenuri di idrogeno, che spesso si dissolvono in acqua per formare acidi idroalici.

Gli alogeni reagiscono anche con l'acqua. La reazione del fluoro con l'acqua è altamente esotermica, producendo acido fluoridrico, un acido forte, e ossigeno. Il cloro, tuttavia, reagisce più lentamente, producendo acido cloridrico e acido ipocloroso, un forte agente ossidante.

Inoltre, gli alogeni possono reagire tra loro, producendo composti binari e covalenti detti composti interalogeni. Per esempio, il bromo reagisce gione visibile. Lo spettro di emissione di ogni elemento è unico e utilizzato per identificare qualitativamente l'elemento.

alogeni

Gli elementi del gruppo 17, noti come alogeni, sono dei non metalli. A temperatura ambiente, il fluoro e il cloro sono gas, il bromo è un liquido e lo iodio un solido. L'astato è un elemento radioattivo altamente instabile, quindi attualmente la maggior parte delle sue proprietà sono sconosciute a causa della sua breve emivita. Anche la tennessina è un elemento sintetico che si prevede faccia parte di questo gruppo.

Gli alogeni non si trovano come singoli atomi ma esistono come molecole biatomiche. Il raggio atomico aumenta dal fluoro allo iodio. La configurazione elettronica del guscio di valenza degli alogeni è ns^2np^5 e hanno la tendenza ad accettare un elettrone per ottenere la configurazione di gas nobile. Le varie proprietà degli alogeni sono elencate nella tabella 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 °C </td>
			<td style="color: black; border: 1px solid black; text-align: center;">Melting Point (°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>

Le affinità elettroniche degli alogeni hanno grandi valori negativi; quindi, gli alogeni sono potenti agenti ossidanti. Il fluoro è l'agente ossidante più potente del gruppo con l'affinità elettronica più negativa. Gli alogeni reagiscono con i metalli per acquisire l'elettrone e produrre il corrispondente alogenuro metallico. Ad esempio, il cloro reagisce con il ferro per dare cloruro di ferro e con il sodio per dare cloruro di sodio. Gli alogeni reagiscono con l'idrogeno per formare alogenuri di idrogeno, che si dissolvono in acqua per produrre degli acidi idroalici. L'acido fluoridrico è l'aloacido più debole. Il fluoro reagisce vigorosamente con l'acqua. La reazione è altamente esotermica e produce ossigeno. La reazione del cloro è meno vigorosa con l'acqua. L'acido ipocloroso prodotto in questa reazione è un forte agente ossidante.

Gli alogeni reagiscono tra loro per formare composti interalogeni, molti dei quali sono composti binari. La formula molecolare generale dei composti interalogeni è ABn, dove A è l'alogeno con numero il atomico più alto ed è un numero dispari. Pochi esempi di composti interalogeni sono ICl, IBr, BrF, BrCl, ClF. Gli alogeni reagiscono con il carbonio per formare composti commercialmente importanti. Ad esempio, l'etilene reagisce con il fluoro per dare perfluoroetilene.

Questo testo è adattato da <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>

Alogeni

Gli elementi del gruppo 17, noti come alogeni, sono non metalli. A temperatura ambiente, il fluoro e il cloro sono gas, il bromo è un liquido e lo iodio un solido. ...

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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

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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