18 electrons fit in just the 3rd energy level, the d subshell.
18 electrons fit in just the 3rd energy level, the d subshell.
how many electrons fit in just the 3rd energy level, the d subshell?
18
bullet::::- each subshell holds at most 10 electrons









































bullet::::- each subshell holds at most 14 electrons









































bullet::::- each subshell holds at most 18 electrons









































therefore, the k shell, which contains only an subshell, can hold up to 2 electrons; the l shell, which contains an and a , can hold up to 2 + 6 = 8 electrons, and so forth; in general, the "n"th shell can hold up to 2"n" electrons.
electron shell
chromium is the fourth transition metal found on the periodic table, and has an electron configuration of [ar] 3d 4s. it is also the first element in the periodic table whose ground-state electron configuration violates the aufbau principle. this occurs again later in the periodic table with other elements and their electron configurations, such as copper, niobium, and molybdenum. this occurs because electrons in the same orbital repel each other due to their like charges. in the previous elements, the energetic cost of promoting an electron to the next higher energy level is too great to compensate for that released by lessening inter-electronic repulsion. however, in the 3d transition metals, the energy gap between the 3d and the next-higher 4s subshell is very small, and because the 3d subshell is more compact than the 4s subshell, inter-electron repulsion is smaller between 4s electrons than between 3d electrons. this lowers the energetic cost of promotion and increases the energy released by it, so that the promotion becomes energetically feasible and one or even two electrons are always promoted to the 4s subshell. (similar promotions happen for every transition metal atom but one, palladium.)
chromium