Atomic structure

• Atomio means indivisible
• J. J Thomson discovered electrons with the help of discharge tube experiment
• Cathode rays consist of material particles
• Cathode rays travel in straight lines
• Cathode rays are deflected by electrical and magnetic fields towards positively charged plate
• Charge to mass ratio of the particles in the cathode rays is independent of the nature of gas taken in the discharge tube
• Cathode rays produce fluorescence when they strike against the wall of the discharge tube
• Cathode rays ionize the gas through which they pass
• Cathode rays produce X-rays when they are made to fall on metals
• Thomson called the negatively charged particles in cathode rays as electrons
• The ratio of charge to mass of an electron is 1.76 x 10^11 C Kg^-1
• Milliken determined the charge of an electron to be -1.602 x 10^-19 Coulombs
• Mass of an electron is 9.10 x 10^-31 Kg
• Discovery of protons occurred when canal rays or anode rays were discovered
• Anode rays travel in straight lines
• Anode rays consist of material particles
• Anode rays are deflected by electrical and magnetic fields towards negatively charged plate
• Charge to mass ratio of the particles in the anode rays depends on the nature of gas taken in the discharge tube
• Charge of a proton is +1.602 x 10^-19 Coulombs
• Mass of a proton is 1.672 x 10^-27 Kg
• James Chadwick discovered neutrons by bombarding a thin sheet of beryllium with alpha particles
• Mass of a neutron is 1.674 x 10^-27 Kg
• Charge of a neutron is 0
• Proton symbol is p+, charge is +1, relative mass is 1, actual mass is 1.67 x 10^-24 g
• Electron symbol is e-, charge is -1, relative mass is 1/1840, actual mass is 9.11 x 10^-28 g
• Neutron symbol is no, charge is 0, relative mass is 1, actual mass is 1.67 x 10^-24 g
• Thomson's model of an atom consists of a uniform sphere of protons with electrons distributed throughout, known as the plum pudding model
• Rutherford's nuclear model of an atom postulates that most of the space in the atom is empty, positive charged protons are concentrated in the nucleus, the size of the nucleus is extremely small compared to the size of an atom, electrons move around the nucleus in circular paths called orbits, and the electrostatic force of attraction between electrons and nucleus is balanced by centrifugal force acting on the electrons
• Atomic number is the total number of protons present in the nucleus of an atom
• Mass number is the number of protons and neutrons present in the nucleus of an atom
• Isotopes are atoms of the same element with the same atomic number but different mass numbers
• Velocity is the distance traveled by a wave in one second
• Wavelength is the distance between two successive crests or troughs
• Frequency is the number of wavelengths in unit length
• Electromagnetic spectrum is the arrangement of all types of electromagnetic radiations in increasing order of wavelength
• Plank's theory of electromagnetic radiation states that electromagnetic radiations are emitted or absorbed discontinuously in the form of packets of energy called photons or quanta
• Black body radiation is emitted by an ideal body that emits and absorbs radiations of all frequencies, and the frequency of emitted radiation depends on temperature
• Photoelectric effect is when certain metals emit electrons when exposed to light, and the number of electrons emitted is proportional to the intensity of incident light
• Threshold frequency is the minimum frequency below which the photoelectric effect is not observed
• Line spectrum of hydrogen includes Lyman series, Balmer series, Paschen series, Bracket series, and Pfund series