Question

The radius of a niobium atom is 131 pm. How many niobium atoms would have to be laid side by side to span a distance of 1.4 mm??

I know that 10^9 is pm or is it -9??

Answer 1

pm is a very small unit, smaller than a head lice. 1 m=10^9 pm, which is the same as 1pm is 10^-9 m

numberatoms*diatmeter atom=1.4mm
numberatoms*131pm=1.4mm
change both to m
numberatoms*131pm*1m/10^9pm)=1.4mm(1m/10^3mm)

number atoms= 1.4*10^9/(131*10^3)
number atoms=1.4 (10^6)/131=1.07*10^4
check that.

Answer 2

1 picometer (pm) is 10^-12 m and 1 millimeter (mm) = 10^-3 m. Thus, (1.4x10^-3)/(131x10^-12) = 1.07 x 10^7 atoms