Tumor markers are measurable biochemicals that are associated with a malignancy. They are either produced by tumor cells (tumor-derived) or by the body in response to tumor cells (tumor-associated). They are typically substances that are released into the circulation and thus measured in the blood.
â For example, the s subshell ( l = 0) contains only one orbital, and therefore the m l of an electron in an s subshell will always be 0. â The p subshell ( l = 1) contains three orbitals, so the m l of an electron in a p subshell will be -1, 0, or 1. â The d subshell ( l = 2) contains Â±ve orbitals, with m l values of -2, -1, 0, 1, and 2.
No matter what its shape, an orbital can only hold a maximum of two electrons at any time. At the lowest energy level, the one closest to the atomic center, there is a single 1s orbital that can hold 2 electrons. At the next energy level, there are four orbitals; a 2s, 2p1, 2p2, and a 2p3. Each of these orbitals can hold 2 electrons, so a total of 8 electrons can be found at this level of energy. In larger and larger atoms, electrons can be found at higher and higher energy levels (e.g. 3s and 3p).