Structure of Atom Test - 6

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.

Towards the end of the 19th century Joseph J.Thomson (1856-1940) was studying electric discharges at the well-known Cavendish laboratory in Cambridge, England. Several people had been studying the intriguing effects in electric discharge tubes before him. Spectacular glows could be observed when a high voltage was applied in a gas volume at low pressure. It was known that the discharge and the glow in the gas were due to something coming from the cathode, the negative pole of the applied high voltage. Thomson made a series of experiments to study the properties of the rays coming from the cathode. He observed that the cathode rays were deflected by both electric and magnetic fields - they were obviously electrically charged. By carefully measuring how the cathode rays were deflected by electric and magnetic fields, Thomson was able to determine the ratio between the electric charge (e) and the mass (m) of the rays. Thomson's result was



The particle that J.J.Thomson discovered in 1897, the electron, is a constituent of all the matter we are surrounded by. All atoms are made of a nucleus and electrons. He received the Nobel Prize in 1906 for the discovery of the electron, the first elementary particle.

Boron is a chemical element with symbol B and atomic number 5. So electronic configuration of boron is 1s²2s²2p¹

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.
  

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

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.

Max Planck theorized that energy was transferred in chunks known as quanta, equal to hν. The variable h is a constant equal to 6.63 × 10^-34 J·s and the variable ν represents the frequency in 1/s.

This equation allows us to calculate the energy of photons, given their frequency.

If the wavelength is given, the energy can be determined by first using the wave equation(c = λ × ν)to find the frequency, then using Planck’s equation to calculate energy.

Cathode rays (also called an electron beam or e-beam) are streams of electrons observed in vacuum tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass behind of the positive electrode is observed to glow, due to electrons emitted from and traveling away from the cathode (the electrode connected to the negative terminal of the voltage supply).

Cathode ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to create the image in a television set

The electron is a subatomic particle, symbol e⁻ or β⁻ , with a negative elementary electric charge.

The electron has a mass that is approximately 11836 that of the proton.

Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm. In terms of frequency, this corresponds to a band in the vicinity of 430–770 THz.