Bromine atomic physical properties

The physical properties of the interhalogens are intermediate between those of their parent halogens. Trends in the chemistry of the interhalogen fluorides can be related to the decrease in bond dissociation energy as the central halogen atom becomes heavier. The fluorides of the heavier halogens are all very reactive bromine trifluoride gas is so reactive that even asbestos burns in it. 

In 1829, the German chemist J.W. Dobereiner classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical properties, and their physical properties varied in an orderly way according to their atomic masses. Table 3.1 shows the atomic mass, density, boiling point, and melting point for each of three elements in the halogen triad—chlorine, bromine, and iodine. Figure 3.1 shows these three elements at room temperature. 

Ddbereiner triads A set of triads of chemically similar elements noted by Jo-hatm Dobereiner (1780-1849) in 1817. Even with the inaccurate atomic mass data of the day it was observed that when each triad was arranged in order of increasing atomic mass, then ffie mass of the central member was approximately the average of the values for the other two. The chemical and physical properties were similarly related. The triads are now recognized as consecutive members of the groups of the periodic table. Examples are lithium, sodium, and potassium calcium, strontium, and barium and chlorine, bromine, and iodine. iiqilElHWJlIHIH. ... 

The halogens are a group of very reactive non-metals. The first three members of the group are chlorine, bromine and iodine. Their atomic and physical properties are summarized in... 

Some of the physical characteristics of the synthesized PPOBr are shown in Table 1. The data in Table 1 indicate that there exists a direct correlation between the degree of bromination of PPO and their physical properties. The densities of PPO increase with an increase in the degree of bromination. The high density of the brominated PPO is attributed to the heavy bromine substituents. The Tg of the brominated PPO was higher than that of unmodified PPO and increase with an increase in the degree of bromination. This is probably due to the reduced torsional motion of the repeat unit caused by the bulky bromine atom. Similar trends have been reported for brominated low molecular weight (0.49 dL/g) PPO [6, 16]. Since polymer with stiff backbones often demonstrate high Tg, one may conclude that bromination of PPO increases polymer chain stiffness. 

There is convincing experimental evidence for the following important statement. To a degree of approximation satisfactory for most analytical work, the mass absorption coefficient of an element is independent of chemical or physical state. This means, for example, that an atom of bromine has the same chance of absorbing an x-ray quantum incident upon it in bromine vapor, completely or partially dissociated in potassium bromide or sodium bromate in liquid or solid bromine. X-ray absorption is predominantly an atomic property. This simplicity is without parallel in absorptiometry. 

The assumption that PBBs and PBDEs share many toxicological characteristics with PCBs also does not consider geometrical differences due to the higher atomic weight and considerably larger molecular volume of bromine compare to chlorine (Hardy 2000, 2002). These differences contribute to dissimilar physical/chemical properties that can influence the relative toxicokinetics and toxicities of the chemicals. 

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