How many copper atoms would you have to line up to make a string 1m long?
According to the source below, the empirical (measured) radius of a copper atom is 135pm (picometers. 1pm = 10e-12m)
Since this is the radius, we need to find the diameter, which is just twice the radius; 270pm
1m / (270x10e-12) = 3.7x10e9, or 3.7 billion atoms.