The term "2p_z" refers to a specific type of atomic orbital in quantum chemistry. It is one of the three p orbitals, which are designated as 2p_x, 2p_y, and 2p_z. The "2" indicates the principal energy level, while the "p" signifies that it is a p-type orbital, characterized by its dumbbell shape. The "z" denotes the orientation of the orbital along the z-axis in a three-dimensional coordinate system. In the context of electron configuration, the 2p_z orbital can hold a maximum of two electrons with opposite spins. Electrons in this orbital are involved in chemical bonding and determine the shape and reactivity of molecules. Understanding the properties of the 2p_z orbital is essential for studying the behavior of elements in the periodic table.