Mwahaha, the sciences, my domain...
The solution to this problem is actually very, very simple.
To find the number of atoms in a given number of moles, we simply multiply by Avogadro's constant.
The value of Avogadro's constant is 6.022 x 10²³
Number of Li atoms = moles x Avogadro's constant
Number of Li atoms = 4.5 x 6.022 x 10²³
Number of Li atoms = 2.7099 x 10²⁴
Number of Li atoms = 2.71 x 