Carbon has six electrons, arranged in the electron configuration 1s2 2s2 2p2. This configuration tells us that there are two electrons in the 1s orbital, two electrons in the 2s orbital, and two electrons in the 2p orbital. The number of shells is determined by the value of the principal quantum number, which is the first number in the electron configuration. In the case of carbon, the principal quantum number is 2, which means that there are two shells.
The first shell (n=1) can hold a maximum of two electrons, which is why the 1s orbital is filled with two electrons in the carbon atom. The second shell (n=2) can hold a maximum of eight electrons, which is why the 2s and 2p orbitals are filled with two electrons each in the carbon atom.
The 2s orbital is a spherical orbital that is centered around the nucleus of the carbon atom. The 2p orbitals are three dumbbell-shaped orbitals that are oriented along the x, y, and z axes. These orbitals are degenerate, which means that they have the same energy level. However, when an external force is applied to the atom, such as when the atom is in a molecule, the degeneracy is lifted and the three 2p orbitals have slightly different energies.
In summary, carbon has two shells, with the first shell containing the 1s orbital and the second shell containing the 2s and 2p orbitals. The 2p orbitals are oriented along the x, y, and z axes and are degenerate in the isolated carbon atom, but have slightly different energies when the atom is in a molecule.