Step-by-step explanation:
Number of moles is the number of particles present in a specific substance. Therefore, we can calculate number of moles as follows.
Number of moles =

Molar mass of Be is 9.0 gram/ mol. Thus, calculate the number of moles of beryllium atoms in 36 g of Be as follows.
Number of moles =
=

= 0.4 mol
Thus, we can conclude that there are 0.4 mol of of beryllium atoms in 36 g of Be.