A sample of copper metal containing 7.738*10^24 atoms is drawn into a cylindrical wire with radius r = 0.625 mm . How long must the wire be in meters?
7.738E24/6.02E23 = mols Cu
g Cu = mols Cu x atomic mass Cu
Look up the density Cu; mass = volume x density and calculate the volume this probably will be in cubic centimeters. I would convert radium in mm to cm, calculate the length in cm and convert to meters.
Then V = (2*pi*r^2)*length