Hey there!
One mole is 6.022 x 10²³ atoms.
We have 0.25 moles.
0.25 x 6.022 x 10²³ = 1.5055 x 10²³
0.25 moles of magnesium contains 1.5055 x 10²³ atoms.
Hope this helps!
i believe the answer is 65°c
Electronic configuration is given by

- 1s orbital is filled
- 2s orbital is unfilled
So