Nucleus and Electronic Configuration of the Carbon Atom

Ground-State Configuration. The element carbon has the symbol C and an atomic number (or Z number) of 6, i.e., the neutral atom has six protons in the nucleus and correspondingly six electrons. In addition the nucleus includes six neutrons (for the carbon-12 isotope). The configuration of the six electrons is that is two electrons are in the K shell 

Quantum Numbers. The notation (or 2s, or 2p ) refers to the quantum numbers necessary to define an orbital.I l The number 1 refers to the K or first shell (principal quantum number) the letter 5 refers to the subshell s (angular momentum quantum number) and the superscript numeral 2 refers to the number of atoms in that subshell. The K shell has only one orbital (the s orbital) and it cannot have more than two electrons. These two electrons, which have opposite spin, are the closest to the nucleus and have the lowest possible energy. The filled K shell is completely stable and its two electrons do not take part in any bonding. 

The next two terms, Is and 2p refer to the four electrons in the L shell. The L shell, when filled, can never have more than eight electrons the element neon has a filled L shell. The L-shell electrons belong to two different subshells, the s and the p, and the 2s and the 2p electrons have different energy levels (the number 2 referring to the L or second shell, and the letters s and p to the orbitals or subshells). The two 2 electrons have opposite spin and the two 2p electrons parallel spin. This view of the carbon atom is represented schematically in Fig. 3.2. 

Note Arrow Indicates direction of electron spin 

Ground State. The configuration of the carbon atom described above refers to the configuration in its ground state, that is, the state where its electrons are in their minimum orbits, as close to the nucleus as they can be, with their lowest energy level, i.e., a single isolated atom. 

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