littleboy

I would like to know how an object can reflect light?Does the object must first absorb a photon with energy equal to the energy difference between two orbitals of atoms,so that it can reflect colour when the excited electron release energy with frequency equal to visible light's frequency? Another question is that where does the energy goes to when an object absorb light which is not the colour the object possess?

Can anyone explain why chlorophyll appears green? Does the green come from excited electrons excited by light(i.e photons with energy equal to the difference between orbitals are emitted)?

I understand what you mean above. But the answer above meanwhile implies that stronger bond leads to a shorter bond length. What I want to ask is that how can we explain the fact that F-F bond has a short bond length but a weak attraction. If F-F bond has a weak attraction,why cant its bond lengthen?

then how can we explain that bond length of C-C is greater than that of C=C ?

What determines the internuclear distance of a covalent compound? What i guess is that the main factor determining the internuclear distance of a covalent compound is the original distance between valence electrons and the nucleus of atoms that the compound derived from(i.e the determinating factor does not include the bond enthalpy) Am i right?

From the book,i know that X-ray is used to determine internuclear distance between atoms in a compound(or element) because wavelength of X-ray is similar to the internuclear distance between 2 atoms.But my question is that:what is the relationship between the nearness and its use to determine the internuclear distance?

Thanks for your help!I know what happens there now!

Thank you very much!

Thanks for your answers but I dont understanding the answer provided to the second question. um....i dont know whether my expression about the second question is clear enough. May I clarifies my second question? My second question is based on a different situation.In the close system,there is no gas expansion,and no plugs......so even the no. of moles of gas molecules inside the container increases,the volume cannot be changed. By PV=nRT where R,V are constant,I would like to ask if no. of moles of gas molecules increase,will T,or P is being changed?

In a close system, when no.of mole of gas molecules increase, gas expansion happens, and its plug is being pushed outward. What i want to ask is that: Where does the energy comes from which does work on the plug?Does the energy come from the vibrational energy or translation energy of the molecules? Another question is that if no gas expansion is allowed in that system,what conclusion can I make by equation PV=nRT?Will the temperature,or the air pressure inside that system keep constant ?

After 1 electron is removed from an specific atom,the successive ionization enthalpy of the specific atom will increase. But what i want to ask is that : Will the emission spectrum of it change?I have this guess because its orbital energy level seems to be changed already.