In the compound mn2o7, what is the oxidation number of manganese?

So in this compound Mn has an oxidation number of +2 while O has an oxidation number of -2 since there are 2 of Mn the total will be +14 and since there are 7 of O the total is -14 (because you will multiply the numbers) so now we will take the +14 and the -14 and the total sum of the two is 0

Qrepresents joules in the formula

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.