The Allegory of the Cave. The dialogue between Socrates and Glaucon is probably fictitious and composed by Plato; whether or not the allegory originated with Socrates, or if Plato is using his mentor as a stand-in for his own idea, is unclear. In the dialogue, Socrates asks Glaucon to imagine a cave, in which prisoners are kept.
The d sublevel consists of five orbitals that can hold a maximum of  two electrons each. The total maximum number of electrons that the  d sublevel can hold is 10 electrons.
The number maximum number of electrons a given orbital will hold are as follows:   * s - 2  * p - 6  * d - 10  * f - 14   Note that this is a maximum number, and it will apply to the suborbitals. For instance, the 1s, the 2s, the 3s and any other s orbital will hold a maximum of 2 electrons. With the p orbital, the 2p, the 3p, and so on all max out at 6 electrons. With the d orbital, it's always gonna be 10 electrons (for the 3d, the 4d, etc.). The f orbital will always be 14 electrons at maximum.