Question

what is a photon? What is valence? What is all-red rochow's principle?

Answer 1

The photon is the fundamental particle of visible light.The photon has zero rest mass and always moves at the speed of light within a vacuum.The photon is a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency.


Valance : the degree of combining power of an element.
Valence is typically the number of electrons needed to fill the outermost shell of an atom. Because exceptions exist, the more general definition of valence is the number of electrons with which a given atom generally bonds or number of bonds an atom forms. (Think iron, which may have a valence of 2 or a valence of 3.)
The IUPAC formal definition of valence is the maximum number of univalent atoms that may combine with an atom.

Allred-Rochow Electronegativity is a measure that determines the values of the electrostatic force exerted by the effective nuclear charge on the valence electrons. The value of the effective nuclear charges is estimated from Slater's rules. The higher charge, the more likely it will attract electrons.