Atomic spectrum shows multiple electronic transitions with characteristic energy lines of the atom. Presence of many spectral lines confirms the existence of multiple energy to which an electron in the ground state can be excited by absorbing energy.
Schrodinger equation of the electron in an atom suggested the possibility of multiple types of wave function and electron density around the nucleus. Each type of wave function is unique in energy, and distribution around the nucleus. Positons of highest electron density of each of the wave function is characterized, by four quantum number. The four quantum numbers gives all the possible energy levels that an electron can be present on excitation in an atom.
As discussed earlier, an electron in an atom
- Has several energy levels (orbitals) of specific energy,
- Each energy level may have sub energy levels (sub-orbitals-s. p.d…),
- Energy of the orbitals are unique and decided by two quantum numbers, named Principle (n) and Azimuthal (l) quantum numbers.
- Sub-orbitals also may have several energy orbitals of similar nature(p, d…). These orbitals are designated by a magnetic quantum number (ml). These orbitals in the same sub energy level are degenerate. The degeneracy is removed under electric or magnetic fields into a number of separate energy levels (orbitals)
- Energy of all the orbitals are quantized and increases in the increasing order of (n + l) value subjected to the condition ‘n’ should be minimum.
- Electronic transitions from one energy level to another is controlled by selection rules or forbidden rules
- Higher energy levels come closer to each other, such that the energy difference becomes smaller with the increase principal quantum number.
- The energy level diagram of electrons in an atom remains similar for all atoms
- The energy of the electron in atom depends on the strength of the attraction of the nucleus on the electron. So, the energy of the electron or energy level decreases with the increasing atomic number