Little is known of the chemistry of astatine, the last member of Group 7A. (a) W

Question

Little is known of the chemistry of astatine, the last member of Group 7A. (a) Which of the following physical characteristics would you expect this halogen and its compounds to have? A. is a nonmetal B. forms the anion At^2- C. reacts with hydrogen to form a basic compound D. reacts with hydrogen to form an acidic compound E. has a high electron affinity F. Lithium astatide has a covalent character. G. has the molecular formula At3 H. Potassium astatide is ionic. I. forms the anion At^- J. has a low electron affinity K. forms the cation At+ L . is a metal M. has the molecular formula At

Explanation / Answer

A . Is a non metal

All halogens are placed at the extreme right side of the periodic table. This is the place dominated by non metals. In general all halogens are non metal and show a high tendency to combine with metals. Therefore based on the position of Astatine on periodic table, we can say that it is a non metal

D. Reacts with hydrogen to form an acidic compound.

All members of halogen family react with hydrogen to form hydrogen halides.

Examples are HF, HCl, HBr, HI etc. All of these compounds are acidic in nature. Therefore following this trend, we can say that astatine would also form an acidic compound with hydrogen .

E. Has high electron affinity.

Electron affinity is the amount of energy released when an electron is added to an atom . In general metals have low electron affinity and non metals have high electron affinity. Among halogen group, At would have least electron affinity but in general if we consider all elements on periodic table, At has high electron affinity value due to its non metallic nature

H. Potassium Astatide is ionic.

Potassium astatide is a compound formed by a metal potassium and a non metal Astatine. Therefore the compound would be ionic in nature

I. Forms the anion At^-

All elements of halogen family have 7 valence electrons. They need 1 more electron to complete their octets. As a result all halogens show a tendency to accept 1 electron and form a negative ion having a charge of -1

M. Has a molecular formula At2

All halogens are divalent. At room temperature F2 and Cl2 are gases, Br2 is liquid and I2 and At2 are solids.

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