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

Halogeny to grupa pięciu pierwiastków niemetalicznych – fluoru, chloru, bromu, jodu i astatu – należących do grupy 17. Halogeny pierwiastkowe występują jako cząsteczki dwuatomowe. 

W temperaturze pokojowej fluor i chlor są gazami, brom jest cieczą, a jod jest ciałem stałym. Mniej wiadomo o właściwościach piątego pierwiastka, astatu, który jest rzadkim i wysoce radioaktywnym ciałem stałym. 

Właściwości fizyczne halogenów, takie jak kolor pierwiastków, zmieniają się w dół grupy. Promienie atomowe rosną wraz ze wzrostem liczby atomowej, a temperatura topnienia i wrzenia wykazują tendencję wzrostową od fluoru do jodu. W przeciwieństwie do tego, właściwości okresowe, takie jak elektroujemność, reaktywność i powinowactwo elektronowe, zmniejszają się w dół grupy.        

Konfiguracje elektronowe halogenów wskazują, że mają one siedem elektronów walencyjnych i brakuje im jednego elektronu do osiągnięcia najbliższej konfiguracji gazu szlachetnego. Dlatego halogeny wykazują wysoką elektroujemność z silną tendencją do pozyskiwania jednego dodatkowego elektronu w celu uzupełnienia swojego oktetu, co czyni je wysoce reaktywnymi i silnymi utleniaczami w porównaniu z innymi grupami.

Fluor jest najsilniejszym utleniaczem wśród halogenów, a jod najmniej.

Halogeny wykazują również bardzo ujemne powinowactwo elektronowe, czyli zmianę energii, gdy elektron jest pozyskiwany przez neutralny atom. Jest ona wyrażona w kJ/mol, a wartość ujemna wskazuje na egzotermiczny charakter reakcji. 

Halogeny reagują z większością metali, dając halogenki metali. Na przykład chlor i sód reagują, tworząc chlorek sodu, który jest związkiem jonowym.

Halogeny reagują z wodorem, tworząc polarne związki kowalencyjne zwane halogenkami wodoru, które często rozpuszczają się w wodzie, tworząc kwasy hydrohalowe. 

Halogeny reagują również z wodą. Reakcja fluoru z wodą jest wysoce egzotermiczna, w wyniku czego powstaje fluorowodór - mocny kwas - i tlen. Chlor jednak reaguje wolniej, wytwarzając kwas solny i kwas podchlorawy - silny środek utleniający. 

Dodatkowo halogeny mogą reagować ze sobą, wytwarzając binarne, kowalencyjne związki zwane związkami międzyhalogenowymi. Na przykład brom reaguje z fluorem, tworząc trifluorek bromu.

halogeny

Pierwiastki z grupy 17, znane jako halogeny, są niemetalami. W temperaturze pokojowej fluor i chlor są gazami, brom jest cieczą, a jod ciałem stałym. Astat jest wysoce niestabilnym pierwiastkiem radioaktywnym, dlatego obecnie większość jego właściwości jest nieznana ze względu na krótki okres półtrwania. Tenes jest pierwiastkiem syntetycznym, który również należy do tej grupy.

Halogeny nie występują jako pojedyncze atomy, ale istnieją jako cząsteczki dwuatomowe. Promień atomowy wzrasta od fluoru do jodu. Konfiguracja elektronowa powłoki walencyjnej halogenów to ns2np5 i mają one tendencję do przyjmowania elektronu w celu uzyskania konfiguracji gazu szlachetnego. Różne właściwości halogenów wymieniono w tabeli 1.

Tabela 1: Właściwości halogenów.

<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;">Pierwiastek</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Konfiguracja elektronowa</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Promień atomowy (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;">Gęstość w 25 °C </td>
			<td style="color: black; border: 1px solid black; text-align: center;">Temperatura topnienia (°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>

Powinowactwa elektronowe halogenów mają duże wartości ujemne; zatem halogeny są silnymi utleniaczami. Fluor jest najsilniejszym utleniaczem z grupy o najbardziej ujemnym powinowactwie elektronowym. Halogeny reagują z metalami, uzyskując elektron i wytwarzając odpowiedni halogenek metalu. Na przykład chlor reaguje z żelazem, dając chlorek żelaza oraz z sodem, dając chlorek sodu. Halogeny reagują z wodorem, tworząc halogenowodory, które rozpuszczają się w wodzie, tworząc kwasy halogenowodorowe. Kwas fluorowodorowy jest najsłabszym halokwasem. Fluor silnie reaguje z wodą. Reakcja ta jest silnie egzotermiczna i wytwarza tlen. Reakcja chloru z wodą jest mniej energiczna, a kwas podchlorawy powstający w tej reakcji jest silnym utleniaczem.


Halogeny reagują ze sobą, tworząc związki międzyhalogenowe, z których wiele to związki binarne. Ogólny wzór cząsteczkowy związków międzyhalogenowych to ABn, gdzie A oznacza halogen o wyższej liczbie atomowej i jest liczbą nieparzystą. Kilka przykładów związków międzyhalogenowych to ICl, IBr, BrF, BrCl, ClF. Halogeny reagują z węglem, tworząc związki ważne z handlowego punktu widzenia. Na przykład etylen reaguje z fluorem, dając perfluoroetylen.

Halogeny

Pierwiastki z grupy 17, znane jako halogeny, to niemetale. W temperaturze pokojowej fluor i chlor są gazami, brom jest cieczą, a jod ciałem stałym. ...

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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.

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Halogens: Trends and Reactions

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