How they came about?, why C is see and not H or He...?
Oh, that. carbon is the atom with 6 protons in its nucleus and, so, 6 electrons in its electron shells. It typically has 6, 7, or 8 neutrons in the nucleus also. The versions with 6 and 7 neutrons are stable and that with 8 is unstable (radioactive).
Hydrogen has one proton in its nucleus and, so, on electron in the electron shells. It can have 0, 1, or 2 neutrons int he nucleus also. The version with 2 neutrons is unstable and those with 0 or 1 are stable.
Helium has two protons in the nucleus and, so, two electrons in the electron shells. It can have one or two neutrons in the nucleus with both versions stable.
The chemical properties of each are determined by the number of electrons and the energy levels they occupy. For example, helium has two electrons, which in their lowest energy state fills up the lowest energy level. That makes helium very inert chemically.
I can go on, but I think you get the picture. The number of protons in the nucleus determine the type of atom and the number of electrons in the atom. The number of neutrons affects how stable the nucleus is. The chemical properties are mostly determined by the number and energies of the electrons.
In bonds between atoms, the electrons are shared. This is a quantum effect the details of which can be determined by solving the Schrodinger equation.
Now, you forgot to say why you think this is relevant to evolution. Evolution is a theory about biology, not chemistry, after all.