A model with all the degrees of freedom of the core and all the radial degrees of freedom of the valence electrons being frozen is used to investigate the qualitative feature of the 3P1e (ground state) and 3P2e states of four-valence-electron atoms (e.g. carbon). The effect of symmetry is emphasized. A number of different correlative densities are defined to inspect the details of correlation and the preference for orientation. The correlation among the electrons is strongly collective and is strongly affected by quantum mechanical symmetry. A gentle oscillation (without node) which transform the system from an equilateral tetrahedron (ET) to a square, and then again to an ET is recognized as a basic mode in this system.