Calculate how many molecules are there in 24.4g of magnesium Calculate how many molecules are there in 2 mols of calcium

The atomic mass of magnesium (Mg) is $24.31 \, \text{g/mol}$.

The formula for moles ($n$) is:
$$
n = \frac{\text{mass (m)}}{\text{molar mass (M)}}
$$
$$
n = \frac{24.4 \, \text{g}}{24.31 \, \text{g/mol}}
$$
$$
n \approx 1.0037 \, \text{mol}
$$

Avogadro's constant ($N_A$) is $6.02 \times 10^{23} \, \text{particles/mol}$.  
The number of molecules ($N$) is given by:
$$
N = n \times N_A
$$
$$
N = 1.0037 \, \text{mol} \times 6.02 \times 10^{23} \, \text{atoms/mol}
$$
$$
N \approx 6.042 \times 10^{23} \, \text{atoms}
$$
There are approximately $\boxed{\text{6.042} \times 10^{23} \text{ atoms}}$ in 24.4g of magnesium.

Avogadro's constant ($N_A$) is $6.02 \times 10^{23} \, \text{particles/mol}$.  
The number of molecules ($N$) is given by:
$$
N = n \times N_A
$$
$$
N = 2 \, \text{mol} \times 6.02 \times 10^{23} \, \text{atoms/mol}
$$
$$
N = 12.04 \times 10^{23} \, \text{atoms}
$$
$$
N = 1.204 \times 10^{24} \, \text{atoms}
$$
There are $\boxed{\text{1.204} \times 10^{24} \text{ atoms}}$ in 2 moles of calcium.