Given properties of nucleus, find its atomic number, mass, and element symbol.

[einsteinoid]

Homework Statement

An unknown nucleus contains 71 neutrons and has twice the volume of the nickel http://www.webassign.net/www32/symImages/f/1/3dca243bf11d1adbce4ca198d1973f.gif nucleus. Identify the unknown nucleus.

Homework Equations

r = (1.2X10^-15)(A^(1/3))
V= (4/3)(pi)(r)^3

The Attempt at a Solution

I plugged 59 into the radius equation and got "4.6715957X10^-15 m"
I then plugged that r value into the volume equation which yielded "4.270555X10^-43"

Since the unknown nucleus is twice the volume of the Ni nucleus, I doubled that volume (getting 8.54111078X10^-43), plugged it into the volume equation to solve for r and got "5.8858 X 10^-15".

Then I plugged that into the original radius equation to solve for A. I keep getting "14.71" which doesn't make any sense to me.

Thanks in advance!

 

[einsteinoid]

Ah i figured it out, nvm.

When I got to the --4.904836 = Cuberoot(A)-- I was supposed to cube the left side of the equation (yeilding 118 as the atomic mass number) but I was tripling it.

Duh!

:-)

 

[rl.bhat]

An unknown nucleus contains 71 neutrons
So for the first nucleus r = (1.2X10^-15)[(71 + Z)^(1/3)] where Z is the number of protons.
Instead of finding radius you can wrote V = k*r = k*A