# Question c514a

Jun 5, 2017

Warning! Long Answer. Here's what I get.

#### Explanation:

Physical Properties

Astatine is a highly radioactive element just below iodine in the Periodic Table.

We can guess at its physical properties by extrapolating from the halogens above it in Group 17.

$\boldsymbol{\text{Property"color(white)(mmmm)"F"color(white)(mmm)"Cl"color(white)(mmm)"Br"color(white)(mmmll)"I"color(white)(mmm)"At}}$

$\text{State at 20 °C"color(white)(mm)"gas"color(white)(mmm)"gas"color(white)(mml)"liquid"color(white)(mmll)"solid"color(white)(mll)"solid}$
$\text{Colour"color(white)(mmmmm)"pale yel"color(white)(m)"grn-yel"color(white)(m) "red-brn"color(white)(mll)"purple"color(white)(m)"black}$

$\text{mp/°C"color(white)(mmmmm)"-220"color(white)(mmm)"-101"color(white)(mm)"-7.2} \textcolor{w h i t e}{m m l l} 114 \textcolor{w h i t e}{m m m} 220$
$\text{bp/°C"color(white)(mmmmml)"-188"color(white)(mmmll)"-35} \textcolor{w h i t e}{m l l} 58.8 \textcolor{w h i t e}{m m l l} 184 \textcolor{w h i t e}{m m m} 310$
$\text{Density/g·cm"^"-3} \textcolor{w h i t e}{m m m m m m m m m m l l} 3.10 \textcolor{w h i t e}{m m m} 4.93 \textcolor{w h i t e}{m m l l} 6.8$

Δ_text(fus)H"/kJ·mol"^"-1"color(white)(ml)0.51color(white)(mmll)6.41color(white)(mll)10.57color(white)(mmm)15.52color(white)(mll)20.5
Δ_text(vap)H"/kJ·mol"^"-1"color(white)(m)6.62color(white)(mml)20.41color(white)(mll)29.96color(white)(mmm)41.57color(white)(mll)53.2

Chemical properties

If astatine behaves like iodine, $\text{At"^"-}$ should be oxidized to ${\text{At}}_{2}$ by sulfuric acid.

4×["2At"^"-" → "At"_2 + "2e"^"-"]
1×["SO"_4^"2-" + "10H"^"+" + "8e"^"-" → "H"_2"S" + 4"H"_2"O"
stackrel(————————————————————)("8At"^"-" + "SO"_4^"2-" + "10H"^"+" → "4At"_2 + "H"_2"S" + 4"H"_2"O")

$\text{8At"^"-" + "SO"_4^"2-" + "10H"^"+" → "4At"_2 + "H"_2"S" + color(white)(mmmmmmmll)4"H"_2"O}$
$\text{8Na"^"+" +color(white)(mmml) "4SO"_4^"2-"→ color(white)(mmmmmmml)"8Na"^"+" + "4SO"_4^"2-}$
stackrel(————————————————————)("8NaAt + 5H"_2"SO"_4 color(white)(mll)→ "4At"_2 + "H"_2"S" + "4Na"_2"SO"_4 +color(white)(mll) 4"H"_2"O")#