Answer
23g of Na, with 6$\times10^{23}$ atoms;
0.5 mol of $H_{2}O_{}$, with 9$\times10^{23}$ atoms.
6$\times10^{23}$ molecules of $N_{2}$, with 12$\times10^{23}$ atoms;
Work Step by Step
1. Find how much atoms we can find in 0.5 mol of $H_{2}O_{}$:
0.5 x 6$\times10^{23}$ = 3 x $10^{23}$ molecules.
Each molecule of $H_{2}O_{}$ has 3 atoms;
(3 x $10^{23}$) x 3 = 9 x $10^{23}$ atoms.
2. Find how much atoms we can find in 23g of Na:
23g of Na $\approx$ 1 mol $\approx$ 6 x $10^{23}$ atoms.
3. Find how much atoms we can find in 6 x $10^{23}$ molecules of $N_{2}$
6 x $10^{23}$ molecules of $N_2$ = 12 x $10^{23}$ atoms of Nitrogen.