Question

1) Extrapolating from your knowlege of the structure of the other halogens (Chlorine = gas, bromine = liquid ,and Iodine = solid), what is likely to be the molecular formula for astatine? Explain.

2) What are the likely physical states of (Gas, liquid, or solid) at room temperature? Explain your answer using your knowledge of the physical states of the other halogens.

a) astatine

b) bromine monoflouride

c) iodine monochloride

Answer 1

The attractive forces between the molecules of noble gas elements increase from top to bottom of the group. The molecules of each element in the group attract each other through London dispersion intermolecular forces.

In fluorine, the electrons are tightly held to the nuclei, so the London dispersion forces are relatively weak. As we know london dispersion forces are between outermost (valence shell) electrons of two atoms.

The London dispersion forces become progressively stronger when we move from top to bottom of this group due to the electrons are further from the nuclei so the electron clouds can more easily distort.

At very low temperatures all molecular motions ceases, hence all appear to be solids, but from room temperature to high temperatures fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid.

a) A molecule of astatine would have two atoms , and the formula of this molecule is At₂.

b) Bromine monofluoride (BrF) is an interhalogen compound and it exist as a gas at room temperature, it is very unstable as bromine atom is bigger in size and fluorine atom is very small in size, due to high electronegativity of fluorine atom it tries to pull the bonding pair of electrons toward fluorine, this makes it very instable.

c) Iodine Monochloride (ICl) is a liquid at room temp. This is due to iodine being a solid, while chlorine is a gas in their elemental states. Their reaction at first produces a gas, and then at room temperature it ends up being collected and contained as a liquid.

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