Question

How many atoms of beryllium are in 1.00 g?

Answer 1

Atomic weight of Beryllium $=9.012g$

The molar mass of Beryllium is therefore$9.012g/mol$

Converting mass$\to$ moles

$1gBe\times$ $1molBe\over9.012gBe$ $=0.1109molBe$

Moles$\to$ Atoms(Multiplying with the Avogadro Constant)

$0.1109molBe\times$ $6.022\times10^{23} atomsBe\over1mol Be$

$=6.678\times 10^{22} atoms Be$