what is the reaction that corresponds to the electron affinity of chlorine, cl?

ELECTRON AFFINITY This page explains what electron affinity is, and and then looks at the factors that impact its size. Information technology assumes that you lot know about simple atomic orbitals, and can write electronic structures for simple atoms.
	Important!If you aren't reasonable happy about atomic orbitals and electronic structures you lot should follow these links before you go whatsoever farther.
First electron analogousness Ionisation energies are e'er concerned with the germination of positive ions. Electron affinities are the negative ion equivalent, and their employ is virtually e'er confined to elements in groups 6 and seven of the Periodic Tabular array. Defining showtime electron affinity The commencement electron analogousness is the energy released when i mole of gaseous atoms each acquire an electron to class ane mole of gaseous one- ions. This is more easily seen in symbol terms. X(g) + e- X-(m) It is the free energy released (per mole of X) when this change happens. Beginning electron affinities have negative values. For example, the beginning electron analogousness of chlorine is -349 kJ mol-1. By convention, the negative sign shows a release of energy. The outset electron affinities of the grouping vii elements F -328 kJ mol-1 Cl -349 kJ mol-ane Br -324 kJ mol-ane I -295 kJ mol-ane
	Note:These values are based on the almost contempo inquiry. If you lot are using a unlike data source, y'all may have slightly unlike numbers. That doesn't matter - the pattern will still be the same.
Is in that location a pattern? Yeah - every bit y'all go down the grouping, start electron affinities become less (in the sense that less energy is evolved when the negative ions are formed). Fluorine breaks that pattern, and volition have to be accounted for separately. The electron analogousness is a measure out of the allure between the incoming electron and the nucleus - the stronger the attraction, the more energy is released. The factors which affect this attraction are exactly the aforementioned equally those relating to ionisation energies - nuclear charge, distance and screening.
	Note:If you haven't read about ionisation energy recently, information technology might exist a expert idea to follow this link earlier you proceed. These factors are discussed in more detail on that page than they are on this one.
The increased nuclear charge as yous go downwards the group is offset by actress screening electrons. Each outer electron in effect feels a pull of 7+ from the heart of the atom, irrespective of which element you are talking nigh. For example, a fluorine atom has an electronic construction of 1s22s22pten ii2py 22pz one. It has 9 protons in the nucleus. The incoming electron enters the 2-level, and is screened from the nucleus by the two 1s2 electrons. It therefore feels a net allure from the nucleus of 7+ (ix protons less the 2 screening electrons). Past contrast, chlorine has the electronic structure 1s22sii2p63stwo3px 23py ii3pz i. It has 17 protons in the nucleus. But once again the incoming electron feels a net attraction from the nucleus of 7+ (17 protons less the ten screening electrons in the first and second levels).
	Notation:If you want to be fussy, there is as well a small-scale amount of screening by the 2s electrons in fluorine and by the 3s electrons in chlorine. This will be approximately the same in both these cases and and then doesn't affect the argument in any manner (apart from complicating it!).
The over-riding factor is therefore the increased distance that the incoming electron finds itself from the nucleus as you become down the group. The greater the altitude, the less the attraction and and then the less energy is released as electron affinity.
	Annotation:Comparison fluorine and chlorine isn't platonic, considering fluorine breaks the trend in the group. However, comparing chlorine and bromine, say, makes things seem more than hard because of the more complicated electronic structures involved. What we take said so far is perfectly true and applies to the fluorine-chlorine instance as much every bit to anything else in the grouping, but there's another gene which operates as well which we haven't considered yet - and that over-rides the consequence of distance in the example of fluorine.
Why is fluorine out of line? The incoming electron is going to be closer to the nucleus in fluorine than in any other of these elements, so you would expect a high value of electron analogousness. Even so, because fluorine is such a small atom, you are putting the new electron into a region of space already crowded with electrons and there is a significant amount of repulsion. This repulsion lessens the attraction the incoming electron feels and then lessens the electron analogousness. A similar reversal of the expected trend happens between oxygen and sulphur in Group 6. The showtime electron analogousness of oxygen (-142 kJ mol-i) is smaller than that of sulphur (-200 kJ mol-1) for exactly the same reason that fluorine's is smaller than chlorine's. Comparing Group 6 and Grouping 7 values As you lot might take noticed, the outset electron analogousness of oxygen (-142 kJ mol-ane) is less than that of fluorine (-328 kJ mol-1). Similarly sulphur'south (-200 kJ mol-1) is less than chlorine's (-349 kJ mol-1). Why? It's simply that the Group 6 element has ane less proton in the nucleus than its next door neighbor in Group 7. The amount of screening is the same in both. That means that the net pull from the nucleus is less in Group 6 than in Grouping seven, and then the electron affinities are less. Starting time electron analogousness and reactivity The reactivity of the elements in group seven falls equally you get down the group - fluorine is the most reactive and iodine the least. Often in their reactions these elements form their negative ions. At GCSE the impression is sometimes given that the fall in reactivity is because the incoming electron is held less strongly as you go down the group and and so the negative ion is less likely to form. That explanation looks reasonable until you include fluorine! An overall reaction will be made up of lots of different steps all involving energy changes, and y'all cannot safely try to explain a trend in terms of simply one of those steps. Fluorine is much more reactive than chlorine (despite the lower electron affinity) considering the energy released in other steps in its reactions more than makes up for the lower corporeality of energy released every bit electron affinity. Second electron analogousness You lot are only ever likely to encounter this with respect to the grouping 6 elements oxygen and sulphur which both form 2- ions. Defining 2d electron analogousness The second electron affinity is the free energy required to add an electron to each ion in 1 mole of gaseous ane- ions to produce one mole of gaseous 2- ions. This is more easily seen in symbol terms. 10-(g) + e- Ten2-(g) It is the energy needed to carry out this modify per mole of X-. Why is energy needed to practice this? You are forcing an electron into an already negative ion. It's not going to go in willingly! The positive sign shows that you have to put in free energy to perform this change. The second electron affinity of oxygen is particularly loftier because the electron is being forced into a small, very electron-dense space. Where would you lot like to go now? To the atomic properties bill of fare . . . To the diminutive structure and bonding carte du jour . . . To Chief Carte du jour . . . © Jim Clark 2000 (last modified October 2021)

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Source: https://www.chemguide.co.uk/atoms/properties/eas.html

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