Answer:
beryllium: 2 valence electrons
nitrogen: 5 valence electrons
oxygen: 6 valence electrons
fluorine: 7 valence electrons
magnesium: 2+ valence electrons
phosphorus: 5 valence electrons
sulfur: 6 valence electrons
chlorine: 7 valence electrons
Explanation:
The elements that form anions will have the electronic configuration similar to the noble gas that is in their period and those that form cations will have a configuration similar to that of the noble gas in the previous period.
He: Be
Ne: F, Al
Ar: Ca, P
Kr: Rb, Se
Answer:

Explanation:
Hello.
In this case, we can solve this problem by applying the Boyle's law which allows us to understand the pressure-volume behavior as a directly proportional relationship:

In such away, knowing the both the initial pressure and volume and the final volume, we can compute the final pressure as shown below:

Consider that the given initial pressure is also equal to Pa:

Which stands for a pressure increase when volume decreases.
Regards.
The equation is:4Al+3O2----2Al2O3