Each electron in an atom is described by four different quantum numbers. The first three (n, l, ml) specify the particular orbital of interest, and the fourth (ms) specifies how many electrons can occupy that orbital.able of Allowed Quantum Numbers. n l ml Number of orbitals Orbital Name Number of electrons 1 0 0 1 1s 2 2 0 0 1 2s 2 1 -1, 0, +1 3 2p 6 3 0 0 1 3s 2 1 -1, 0, +1 3 3p 6 2 -2, -1, 0, +1, +2 5 3d 10 4 0 0 1 4s 2 1 -1, 0, +1 3 4p 6 2 -2, -1, 0, +1, +2 5 4d 10 3 -3, -2, -1, 0, +1, +2, +3 7 4f 14.
Rat droppings are a key sign of a rat infestation; the mess and debris they leave in their wake is unmistakable. In addition to scattered nesting materials; debris from chewing, feeding and gnawing; rodents excrete urine and feces every few steps they take along their habitual paths of travel.
The best-known rat species are the black rat (Rattus rattus) and the brown rat (Rattus norvegicus). The group is generally known as the Old World rats or true rats, and originated in Asia. Rats are bigger than most Old World mice, which are their relatives, but seldom weigh over 500 grams (1.1 lb) in the wild.