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 box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.