ELECTRONIC STRUCTURE OF MATTER

• Joseph John Thomson conducted an experiment using the cathode ray tube. His experiments resulted in the discovery of the electron. He named his atomic model as the nuclear model of the atom.
• when barium chloride heated it produces green color because the metallic element barium is responsible for that color while copper chloride produces a blue color because the metallic copper emits that color
• Light is a radiant energy travelling in space through a wave form. Each radiation is characterized by a wavelength and amplitude.
• The wavelength is the distance between two successive crests while the amplitude is the height of the wave. The wavelength determines the amount of energy it carries.
• The shorter the wavelength the higher the energy.
• Name of elements - Flame Color

  Sodium - Yellow

  Copper - Green

  Lithium - Light Red

  Lead - Pale Blue

  Calcium - Brick Red
• Niels Bohr explained that each atomic spectra of elements indicates the transformation of energy within the atom. He concluded that the electrons as particle that are moving around the nucleus with fixed energy where he called as energy level. But in a more sensitive spectroscope finer lines are seen within each line of color. It means that each main energy level in an atom consists of sublevels
• When the electron is on its ground state there is an absorption of energy, the electron jumps to a higher energy level. Then, as the electron goes back to its original energy level, it will release energy.
• Main Energy Level - Sublevels

  1 or K - s

  2 or L - s,p

  3 or M - s. p, d

  4 or N - s.p.d.f

  5 or O - s.p.d.f

  6 or P - s. p, d

  7 or Q - s,p
• The main energy level is made up of sublevels of energy in which the energy level is made up of one or more sublevels.
• Heisenberg’s Uncertainty Principle states that it is not possible to determine the exact location and velocity of an electron in an orbital at the same time. But there is a probability that the electron will be in a certain region in an atom which is called as the electron cloud. It is also described as the region composed of negatives surrounding the nucleus associated with the atomic orbital.
• The Quantum Mechanical Model was introduced by Schrodinger. This model shows how likely an electron can be found around the nucleus. It looks like a cloud of negative charges having a certain geometrical figure.
• The Quantum Mechanical Model also gives the information about the energy of the electron. It also describes region of space around the nucleus as consisting of shells it is also called the principal or main energy levels.
• There are different kinds of Quantum Numbers:

  1. Principal quantum number (n) describes the energy level of an electron in an atom. It can be expressed using the letters of an alphabet like K, L, M, N, O, P and Q energy level.
  2. Angular Momentum Quantum Number (l) it describes the way on how the electrons move around the nucleus. It determines the shape of an orbital.
• There are different kinds of Quantum Numbers:

  
  

  3. Magnetic Quantum Number (ml) it refers to the possible behavior of the electrons in a magnetic field.
• There are different kinds of Quantum Numbers:

  
  

  4. Spin Quantum Number (ms) describes the rotations or the spins on how the electrons move on their own axis as they move around the nucleus. The spinning charge create the magnetic field that make the electron comparable to a magnet. The electron spinning clockwise has the - ½ values. The electrons that are spinning counter - clockwise have the + ½ values.
• Rules Governing Electronic Configuration

  1. The Aufbau Principle requires that the electrons occupy the lowest possible energy level before filling up the next.
  2. Pauli’s Exclusion Principle states that no two electrons can have the same set of four quantum number; the spin quantum number limits the number of electrons in an orbital to a maximum of two.
  3. Hund’s Rule requires that the electrons fill the orbitals in a sub level, one by one, before pairing the electrons in an orbitals spin in opposite direction.
• You can also use the electron configuration to identify some of the information about the elements in terms of the following like the group number, the period number, the number of paired and unpaired electrons and also the valence electrons.