1.2 x 10^10 mm^3 is equivalent to 12.0 m^3
The average speed is calculated using the following formula
Where

T = 298 K [room temperature]
m = mass of each molecule of oxygen
mass of one mole of oxygen molecules = 32 g / mol
mass of one molecule of oxygen will be = 
mass of one molecule of oxygen will be = 
putting values
average speed = 
Average speed = 482.19 m / s
average speed = 1735.8 km / h
so approx = 1700 km/h
Explanation:
neon has 8valence electrons
chroline has 7 valence electrons
nitrogen has 5 valence electrons
oxygen has 6 valence electrons
so neon has the most valence elctrons