Polonium, the period 6 member of group 6a(16), is a rare radioactive metal that is the only element with a crystal structure based on the simple cubic unit cell. if its density is 9.232 g/cm3, calculate an approximate atomic radius for polonium―209.

Approximate atomic radius for polonium-209 is 167.5 pm .

Explanation:

Number of atom in simple cubic unit cell = Z = 1

Density of platinum =

Edge length of cubic unit cell= a = ?

Atomic mass of Po (M) = 209 g/mol

Formula used :  

where,

ρ = density

Z = number of atom in unit cell

M = atomic mass

= Avogadro's number  

a = edge length of unit cell

On substituting all the given values , we will get the value of 'a'.

Atomic radius of the polonium in unit cell = r

r = 0.5a

Approximate atomic radius for polonium-209 is 167.5 pm.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form