Fluorine electron affinity

One surprising physical property of fluorine is its electron affinity which, at — 333 kJmoPS is lower than that of chlorine, -364 kJmol , indicating that the reaction X(g) + -> X (g) is more... 

Bromine has a lower electron affinity and electrode potential than chlorine but is still a very reactive element. It combines violently with alkali metals and reacts spontaneously with phosphorus, arsenic and antimony. When heated it reacts with many other elements, including gold, but it does not attack platinum, and silver forms a protective film of silver bromide. Because of the strong oxidising properties, bromine, like fluorine and chlorine, tends to form compounds with the electropositive element in a high oxidation state. 

The energy change of reaction (12) is called the electron affinity of the fluorine atom. It is symbolized by E and, as defined here, is a negative quantity if heat is released when the ion is formed ... 

Electron affinities are difficult to measure and are known reliably for only a small fraction of the hundred or so elements. The electron affinity of fluorine is one that is known ... 

The neutral fluorine atom has seven valence electrons that is, seven electrons occupy the highest partially filled cluster of energy levels. This cluster of energy levels thus contains one fewer electron than its capacity permits. The electron affinity of fluorine shows that the addition of this last electron is energetically favored. This is in accord with much other experience which shows that there is a special stability to the inert gas electron population. 

In view of the electron affinity of a fluorine atom, we can speculate on what would be the result of a collision between two fluorine atoms. Will a reaction occur The energy is one of the factors which determines the answer. First let us consider a reaction that does not occur spontaneously. 

Now we can say why the chemical bond forms between two fluorine atoms. First, the electron affinity of a fluorine atom makes it energetically favorable to acquire one more electron. Two fluorine atoms can realize a part of this energy stability by sharing electrons. All chemical bonds form because one or more electrons are placed so as to feel electrostatic attraction to two or more positive nuclei simultaneously. 

Self-Test 1.15B Account for the large decrease in electron affinity between fluorine and neon. 

Which element of each of the following pairs has the higher electron affinity (a) oxygen or fluorine (b) nitrogen or carbon (c) chlorine or bromine (d) lithium or sodium ... 

A neutral atom can add an electron to form an anion. The energy change when an electron is added to an atom is called the electron affinity (EA). Both ionization energy (IE) and electron affinity measure the stability of a bound electron, but for different species. Here, for example, are the values for fluorine ... 

Return to the case of LiF. Lithium ionizes readily, but has little affinity for electrons (I = ionization energy = 5.4 eV and A = electron affinity = 0eV.). On the other hand, fluorine is difficult to ionize, but has considerable electron affinity (I = 17.4eV. and A = -3.6eV.). Thus, when Li and F atoms are close neighbors, electrons can transfer to make Li+ and I. These then attract electrostatically until compression of their ion-cores prevent them from contracting further. In a solid crystal, there are both attractive +/- pairs, and repulsive (+/+ as well as -/-) pairs. However, for large arrays, there is a net attraction. This can be shown most simply by examining a linear chain of +q, and -q charges (Kittel, 1966). 

Although the electron affinity of fluorine is less than that of chlorine, F2 is more reactive than Cl2. Explain some of the reasons for this difference in reactivity. 

The electron affinity (EA) of fluorine can be estimated from the first two entries of Table 2.2 as follows ... 

Fc/Fc+) have been obtained, irrespective of the number of bridging thiophene rings [56]. Naito et al. [239] compared a variety of other electron-transport materials by their ionization potential and electron affinity measured by different methods. For example, some bis(styrylanthracenes) similar to 21 but with electron-withdrawing groups exhibit higher electron affinities than Alq3. The per-fluorinated compounds 19 and 34 showed irreversible electroreductions [62]. 

One surprising physical property of fluorine is its electron affinity which, at — 333 kJmol is lower than that of chlorine, —364 kJmol-1, indicating that the reaction X(g) + e - X (g) is more exothermic for chlorine atoms. In view of the greater reactivity of fluorine a much higher electron affinity might reasonably have been expected. The explanation of this anomaly is found when the steps involved in a complete reaction are considered. For example, with a Group I metal ion M+(g) the steps to form a crystalline solid are,... 

Fluorine is a highly reactive element. The relative ease with which it gains an electron when it forms bonds is reflected in its high electron affinity. 

---