Among the choices above, I think the statement that best describes an intensive property of matter is letter B which is " It depends on how a substance was formed." <span>Intensive properties are those property which does not depend upon the amount of substance present in the system. Such as refractive-index, density etc </span>
Answer : The frequency of a photon of radiation is, 
Explanation : Given,
Wavelength of the radiation = 670.8 nm
First we have to convert wavelength form 'nm' to 'm'.
Conversion used : 
So, the wavelength of the radiation = 670.8 nm = 
Now we have to calculate the frequency of a photon of radiation.
Formula used : 
where,
= frequency of a photon of radiation
= wavelength of the radiation
c = speed of light = 
Now put all the given values in the above formula, we get the frequency of a photon of radiation.


Therefore, the frequency of a photon of radiation is, 
Answer: The valency of oxygen is 2, because it needs two atoms of hydrogen to form water.
Explanation: The nearest noble gas to magnesium is neon with electronic configuration of [2,8], to achieve this stable electronic configuration Mg can lose 2 valence electrons, hence its valency is 2 + ^+ +