Structure of Atom Test - 7

In 1920, Otto Stern and Walter Gerlach designed an experiment, which unintentionally led to the discovery that electrons have their own individual, continuous spin even as they move along their orbital of an atom. The experiment mentioned above by Otto Stern and Walter Gerlach was done with silver which was put in an oven and vaporized. The result was that silver atoms formed a beam that passed through a magnetic field in which it split in two.

Probability density of finding an electron at a point with in an atom, it is posible to predict region around the nucleus where electron can most probably be found.

ψ has no physical significance while ψ² represnts the probability density of finding an electron.

Shielding effect can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces of the electrons on the nucleus. It is also referred to as the screening effect (or) atomic shielding.

The Aufbau Principle states that in the ground state of an atom, an electron enters the orbital with lowest energy first and subsequent electrons are fed in the order of increasing energies. The word 'aufbau' in German means 'building up'. Here, it refers to the filling up of orbitals with electrons.

The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.

Daltons theory said atom is indivisible in nature so it doesnot explain the existence of subatomic particles.

The indivisibility of an atom was proved wrong: an atom can be further subdivided into protons, neutrons and electrons. However an atom is the smallest particle that takes part in chemical reactions.

The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). The experiment entailed observing tiny electrically charged droplets of oil located between two parallel metal surfaces, forming the plates of a capacitor.

Number of protons =  Atomic number =6

Number of neutrons = atomic mass - no of protons = 13-6 = 7

Production of cathode rays Cathode rays are produced in the discharge tube by applying the following conditions:

• A high potential difference (>1200 V) is applied across the two aluminium electrodes.
• The length of the tube is 30 cm and the diameter is 3 cm.
• Pressure inside the tube is maintained below 0.01 mm of Hg.

Electron was discovered by J. J. Thomson in 1897 when he was studying the properties of cathode ray. J. J. Thomson won Nobel Prize in 1906 for discovering the elementary particle electron.