An atom of oxygen has six electrons in its outermost ring and requires two more to become stable. What is the valence number of oxygen

Oxygen in its natural state has 6 valence electrons.

Explanation: The atomic number/ proton number of oxygen is 8, as seen on the periodic table. This is equal to the electron number.

This means there are 2 electrons in the core s shell (innermost), and 6 electrons in the p shell (outermost).

Valence electrons are the electrons found in the outermost shell, so Oxygen has 6 valence electrons.

I don't know if you've been taught electron configuration, but Oxygen's electron configuration is: . The 2s and 2p are orbitals of the outermost ring in Oxygen, so adding 2+4 = 6 valence electrons.

93.2 ml + 3920 ml = 4013 ml total  

(93.2 ml) * (2.03 m) / (4013 ml) = 0.0471 m

the volume in in l of the diluted solution would be 0.0471 m.

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.