Energy level:

Energy level can be definite as stable energy that a physical system can have; used especially of the state of electrons in atoms or molecules. Energy level The discrete energy state of an electron in an atom or molecule. Electrons can occupy specific energy levels only and jump from one energy level to another. The lowest energy level is known as ground state of the atom or molecule. Within the atom, energy levels correspond to the distance from the nucleus. The electron requires energy to jump from a state of the lower energy which is an energy level close to the nucleus to a higher energy level which is an energy level away from the nucleus. At this state the atom is then said to be excited. Energy levels can be defined by a quantum number denoted by n. As an electron in an atom has both mass and motion, it contains two types of energy. By the virtue of its motion the electron contains kinetic energy. Because of its position it has potential energy. The total energy contained by an electron determines the radius of the electron orbit.  In every principal energy level, there is at least one sublevel. The number of sublevels is equal to principal quantum number. the 1st principal energy level has one sublevel and is called as 's' sublevel while the second principal energy level has two sublevels and is called as 'p' sublevel. There are s, p, d, f, g, h, and many more sublevels.  An orbital is the region within the sublevel where electrons may be found. In each orbital, there can be a maximum of 2 electrons. Each s sublevel posses single orbital. Each p sublevel has 3 orbitals, each d sublevel has five orbitals, and each f sublevel has sevenorbitals. Thus, any s sublevel can have two electrons, while any p sublevel can have six electrons.