Chemistry PDF

Dalton’s Atomic Theory Thomson’s Model Conclusion of Rutherford Experiment 1. Atom is the smallest particle of any 1. Thomson proposed Most of the space insid...

Dalton’s Atomic Theory Thomson’s Model Conclusion of Rutherford Experiment 1. Atom is the smallest particle of any 1. Thomson proposed Most of the space inside the atom is empty because substance which cannot be divided that an atom consists Atomic structure most of the a-particles passed through the gold foil further. 2. Atoms can neither be created nor of a uniform sphere of without getting deflected. 2. The mass of an atom is uniformly destroyed, only the rearrangement of positive charge in As a few alpha particles suffered minor deflections distributed over the atom. atoms occur in a chemical reaction. which the electrons are & a very few major deflections, this means that 3. All the atoms are hard and dense. embedded. these must have met with some obstruction in their 4. All the atoms of an element are Wave Characteristics path. identical in all respect but atoms of A very small fraction of α-particles were deflected different elements are different. l 1) Wavelength- It is defined as the distance by 180o, indicating that all the positive charge and Result of Thomson experiment between two nearest crests or nearest troughs. mass of the gold atom was concentrated in a very 2) Wave number (തv) : It is defined as number small volume within the atom. 1. They travel in a straight line in of waves per unit length. 1 m → 1/l waves absence of Electric or Magnetic fields. Rutherford regarded this very small, dense & It is measured in terms of cm–1, m–1 etc. positively charged obstruction in an atom as 2. Electric and Magnetic factors cause deflection of these cathode rays. 3) Frequency (n): Frequency of a wave is defined as the number of nucleus (means centre). 3. These rays deflect like a negatively waves which pass through a point in 1 sec. The electrons with negligible mass & negative charged particle. 1 Hertz = 1 sec–1 charge were supposed to be present in the portion 4. Deflection is dependent on strength of 4) Time period (T): Time taken by a wave to pass through one point. around nucleus known as extra nuclear portion. Electric charge or Magnetic fields. Or time taken by a wave to complete distance of one wavelength Rutherford Atomic Model charge 1 1. Like charges repel each other. = 1.758820 x 10−11 C Kg −1 T = sec mass v 2. Mass of atoms was approximately 5) Velocity → (c) Velocity of a wave is defined as distance covered coming out to be double the mass of Charge on Electron = 1.602 x 10−19 C by a wave in 1 sec. protons. 6) Amplitude → (a) It is the height of the crest or depth of the trough of Drawbacks of Rutherford model a wave This theory could not explain the stability of an X-Rays Given by Wilhelm Rontgen atom. According to Maxwell, accelerated electron loses its energy continuously in the form of When electrons strike a material in the cathode ray tube, they produce rays which can cause electromagnetic radiations. fluorescence in the material placed outside the cathode ray tube. These Radiations are called X-Rays. Electron (e) Negatively charged. Mass 9.1 x 10-31 Kg Radioactivity Given by Henri Becquerel, Marie Curie Proton (p) Positively charged. Mass 1.672 x 10-27 Kg Certain elements emit radiation on their own and this phenomenon is called Radioactivity. Neutron (n) Neutral. Mass 1.675 x 10-27 Kg Black Body Radiation Planck’s Theory Atomic structure The radiant energy emitted or absorbed by a body is not radiated continuously but discontinuously in the form of small discrete packets of energy. These packets are called quantum. E ∝ ν E = hν hc E = λ h = 6.6 × 10−34Joule sec Total amount of energy transmitted from one body Wein’s Displacement Law 𝒃 to another will be some integral multiple of 𝝀𝐦𝐚𝐱 = energy of a quantum. 𝑻 𝛌𝐓 = 𝐛 E = nhν 𝐛 = 2.898 x 10-3 m-K Where n is an integer and n = number of quantum 𝛌𝟏 𝐓𝟏 = 𝛌𝟐 𝐓𝟐 = 𝛌𝟑 𝐓𝟑 8𝛱ℎ𝑐 2 1 𝐸𝜆 = 𝜆5 𝑒 ℎ𝑐Τ𝜆𝑘𝑡 − 1 Area under the graph gives total energy Higher temperature means more radiations