Electron Configuration

The electron configuration of an atom is where the electrons are found and how many there are in an atom. There are four levels to describe the location of an electron in an atom: principle energy level, sublevel, orbitals, and spin. The principle energy level describes how far away from the nucleus an electron can be found. Its symbol is n. There are four different sublevels, s, p, d, and f. The first principle energy level only has one sublevel, the 1s sublevel. The second principle energy level has two sublevels, 2s and 2p. The third principle energy level has three sublevels, 3s, 3p, and 3d. The fourth and all subsequent principal energy levels have four sublevels, 4s, 4p, 4d, and 4f. Each sublevel ahs a specific number of orbitals, the s sublevel has one orbital that can hold 2 electrons, shaped like a sphere, the p sublevel has 3 orbitals that can hold 6 electrons, shaped like dumb-bells orientated perpendicular to each other around the x, y, and z axis, the d sublevel has 5 orbitals that can hold 10 electrons, and the f sublevel has 7 orbitals and can hold 14 electrons, both the d and f sublevels have complex shapes. Each electron is paired with another and they have opposite spins. 

When writing the electron configuration of an element the first number is the principle energy level then the sublevel then the number of electrons is the superscript. This link gives you practice writing the electron configuration for different elements.