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

Os halogéneos são um grupo de cinco elementos não metálicos flúor, cloro, bromo, iodo e ástato pertencentes ao Grupo 17. Os halogéneos elementares existem como moléculas diatómicas. À temperatura ambiente, o flúor e o cloro são gases, o bromo é um líquido e o iodo é um sólido.Sabe-se menos sobre as propriedades do quinto elemento, ástato, que é um sólido raro e altamente radioativo. As propriedades físicas dos halogéneos, tais como a cor elementar, variam consoante o grupo. Os raios atómicos aumentam com o aumento do número atómico, e o ponto de fusão e o ponto de ebulição mostram uma tendência ascendente do flúor para o iodo.Pelo contrário, as propriedades periódicas como a eletronegatividade, a reatividade e a afinidade dos elétrons diminuem pelo grupo abaixo. As configurações dos elétrons dos halogéneos indicam que têm sete elétrons de valência e estão a um elétron de atingirem as suas configurações de gases nobres. Por conseguinte, os halogéneos exibem elevadas eletronegatividades com uma forte tendência para ganhar um elétron adicional para completar o seu octeto, tornando-os agentes oxidantes altamente reativos e poderosos em comparação com outros grupos.O flúor é o agente oxidante mais potente entre os halógenos e o iodo o menos. Os halogéneos também exibem afinidades de elétrons altamente negativas, que é a alteração na energia quando um elétron é ganho por um átomo neutro. É expresso em kilojoules-por-mol, e o valor negativo indica a natureza exotérmica da reação.Os halogéneos reagem com a maioria dos metais para produzir halogéneos metálicos. Por exemplo, o cloro e o sódio reagem para produzir cloreto de sódio, que é um composto iônico. Os halógenos reagem com o hidrogênio para formar compostos polares covalentes chamados de halogenetos de hidrogênio, que se dissolvem frequentemente na água para formarem ácidos hidrácidos.Os halógenos também reagem com a água. A reação do flúor com a água é altamente exotérmica, produzindo fluoreto de hidrogênio um ácido forte e oxigénio. O cloro, no entanto, reage mais lentamente, produzindo ácido clorídrico e ácido hipocloroso um forte agente oxidante.Para além disso, os halogéneos podem reagir uns com os outros, produzindo compostos binários e covalentes chamados de compostos interalógicos. Por exemplo, o bromo reage com o flúor formando o trifluoreto de bromo.

halogénios

Os elementos do grupo 17, conhecidos como halogénios, são não-metais. À temperatura ambiente, o flúor e o cloro são gases, o bromo é um líquido, e o iodo é um sólido. O astatínio é um elemento radioativo altamente instável, pelo que hoje em dia a maioria das suas propriedades são desconhecidas devido à sua meia-vida curta. O tenesso é um elemento sintético também previsto estar neste grupo. 

Os halogénios não são encontrados como átomos únicos, mas existem como moléculas diatómicas. O raio atómico aumenta do flúor para o iodo. A configuração eletrónica da camada de valência dos halogénios é ns2np5, e eles têm tendência a aceitar um eletrão para alcançar a configuração de gás nobre.  As várias propriedades dos halogénios estão listadas na tabela 1.

Tabela 1: Propriedades dos Halogénios.

<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;">Elemento</td>
<td style="color: black; border: 1px solid black; text-align: center;">Configuração Eletrónica</td>
<td style="color: black; border: 1px solid black; text-align: center;">Raio Atómico (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;">Densidade a 25 °C </td>
<td style="color: black; border: 1px solid black; text-align: center;">Ponto de Fusão (°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>

As afinidades eletrónicas dos halogénios têm grandes valores negativos; portanto, os halogénios são poderosos agentes oxidantes. O flúor é o agente oxidante mais potente do grupo com a afinidade eletrónica mais negativa. Os halogénios reagem com metais para ganhar o eletrão e produzir haletos metálicos correspondentes. Por exemplo, o cloro reage com o ferro para dar cloreto de ferro e com o sódio para dar cloreto de sódio. Os halogénios reagem com hidrogénio para formar haletos de hidrogénio, que se dissolvem em água para produzir ácidos hidrohálicos. O ácido fluorídrico é o haloácido mais fraco. O flúor reage vigorosamente com água. A reação é altamente exotérmica e produz oxigénio. A reação do cloro é menos vigorosa com a água. O ácido hipocloroso produzido nesta reação é um agente oxidante forte.

Os halogénios reagem uns com os outros para formar compostos interhalogénicos, muitos dos quais são compostos binários. A fórmula molecular geral para compostos interhalogénicos é ABn, onde A é o halogénio com maior número atómico e é um número ímpar. Alguns exemplos de compostos interhalogénicos são ICl, IBr, BrF, BrCl, ClF. Os halogénios reagem com carbono para formar compostos comercialmente importantes.  Por exemplo, o etileno reage com o flúor para dar perfluoroetileno.

Este texto é adaptado de <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>

Halogénios

Os elementos do grupo 17, conhecidos como halogênios, são não metais. À temperatura ambiente, o flúor e o cloro são gases, o bromo é um líquido e o iodo um sólido. ...

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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

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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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Nomenclature of Alkanes

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Understand types, properties, and structure of matter.

Halogens: Trends and Reactions

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