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Note On Atomic Structure Class 11

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Published in: Chemistry
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Upgraded material on "ATOMIC STRUCTURE" for NEET & IIT JEE Foundation course.

SK S / Chennai

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Qualification: M.Sc , B. Sc Chemistry Honours

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  1. S.K. Sir The Ilonue of Chennistry Since-2005 [email protected] tomnc Structure SoKo Nothing Less Than Success
  2. Particle And Electrical Nature of Matter Faraday's First Law Faraday's Second Law S.K. Sir The weight of an element liberated at the electrode during electrolysis is directly proportional to the quantity of electricity passed When the same current is passed through different electrolytes, then the number of moles of various substances liberated at an electrode are in the ratio of small integers Cathode cu —cu2+ s02— [email protected] The Ilon•e of Chemistry
  3. C A H O D E They cast shadows of Solid objects placed in their Path. Hence they travelled in straight line When allowed to fall on a light paddle wheel placed in their path, cause rotation of the wheel. Hence, they made up of material particles. They are attracted to the (+) ve plate when two charged plates are on either side of them. Hence they are made up of (-) ve particles. They get deflected in a magnetic field in a direction as to indicate, they are negatively char ed. They heat a metal foil placed between the electrodes. These rays ionize the gas through which they pass. They produce X- Rays on striking against a hard metallic surface like Tungsten. Like ordinary light, they affect photographic plates. They cause fluorescence on striking substances such as Zinc Sulphide. They can penetrate thin sheet of metals or Mica but are stopped by thick sheets. They cause chemical changes as they act as Reducing Agents. Name Suggested By Stoney They possess same e/m ratio regardless of the nature of the material taken for electrode or gas RAYS taken in the tube. Modern Name Electron Beam S.K. Sir [email protected] The I Iome of Chemistry Cathode Discharge Tube Air at very Anode low pressure Cathode rays 1 To Vacuum Pump High Voltage Generator
  4. Millikan's Oil Drop Experiment a The experimental apparatus is patterned after the original apparatus, made and used by R.A. Millikan, in 1909, to show that electric charge exists as integral multiples of "e" the charge on a single electron. Apparatus: Millikan and Fletcher designed the experiment apparatus. It included two metal plates held at a distance by an insulated rod. There were four holes in the plate, three of which were there to allow light to pass through, and one was there to allow viewing through the microscope. C] He sprayed a fine mist of oil droplets above a pair of parallel metal plates, the top one which had small hole on it. Some of the oil drops passed through this hole into the space between the plates. C] He irradiated the air between the plates briefly with X-rays. The X-rays knocked out the electrons from the air molecules. These electrons were picked up by the oil droplets thereby giving them a negative charge. By observing the rate of fail of the charged drops both when the metal plates were electrically charged and when they were not. He was able to calculate the amount of charge carried by each drop. After repeating his experiment many times, he evaluated the value of charge carried by each electron. Cl Using the apparatus, he was able to calculate the charge on an electron as 1.60 x 10-19 c. Conclusion: This experiment is one of the most fundamental of the experiments in the undergraduate laboratory. The experimental apparatus is patterned after the original apparatus, made and used by R.A. Millikan to show that electric charge exists as integral multiples of "e" the charge on a single electron. Oil sprayed in fine droplets Pinhole Xray to produce charge on droplet Telesco ic eyepiece [email protected] Electrically charged bras plates ELECTRODE Charged oil droplet under observation S.K. Sir The I Iorne of Chemist ry
  5. Thomson's Ex enment S.K. Sir The Home of Chemistry He used a cathode ray-tube quite similar to present day TV picture tube to measure the ratio of the charge to mass of an electron. The electron generated at the cathode are accelerated towards the Anode which has a hole on it. Some of the electrons pass through the hole and strike the phosphor ( a chemical that glows on electron striking on it) coated face of the tube, producing a bright spot. He also fitted the neck of the tube with magnet and a pair of metal plates which could be given electrical charges. In the absence of magnetic field, the beam of electrons is deflected towards the positive plate. The amount of deflection is proportional to the charge on the particle. It is inversely proportional to the mass of particle because a heavy particle will be less affected by the electrostatic field as it passes between the plates than a lighter particle. If a magnetic field is generated at Right angles to the electric field, the electrons are deflected in a direction exactly opposite to that caused by the electrically charged plates. By carefully controlling the charge on the plates when the plates and the magnet were both around the tube, he was able to cancel the magnetic field effect that tends to deflection in the opposite direction. C) By measuring the strengths of magnetic and electric field needed Cathode Anode to balance each other, Thomson was able to measure the e/m rati Thomson was NOT able to measure the charge or mass alone. ratio of electron — ratio of proton -19 -31 -19 -27 elm ratio of Electron -1.75 x 1011 C/kg [email protected] c X, Fluorescent screen Magnet
  6. ANODE Rays They travel in straight line and cast shadows of the object placed in their path. C] They affect the photographic plates and cause fluorescence. Like Cathode Rays, these rays also rotate a paddle wheel placed in their path. S.K. Sir They heat the metals on which they fall. The I-Iome of Chemistry C] These rays are deflected by electronic and magnetic fields just like cathode rays. However, deflection of these rays is opposite to that of cathode rays. Hence these rays are made positively charged particles. e/m Ratio for all positive rays is not the same and depends upon the nature of the gas taken in the discharge tube. Atom Air at very low Pressure Red Glow Electron Proton Neutron Discharge tube Anode cathode High voltage To vaccum generator pump Production of Anode Rays [email protected]
  7. [email protected] Electron Vs Proton Vs Neutron Head Discoverer Location Charge Mass Mass of One Mole Charge of one mole of Density S.K. Sir The Ilmne of Chemistry Electron J. J. Thomson Orbit or Sub-shell Proton E. Goldstein Nucleus (-) ve 1.6 x 10-19 Coulombs (+) ve 1.6 x 10-19 Coulombs 9.1x 10-31 kg 0.55 mgm 96500 Coulombs = One Faraday 2.17 x 1020 kg/m3 Proton & Neutron are made up of QUARK 1.67262 x 10-27 kg 1.007 gm 96500 Coulombs = One Faraday 1018 kg/m3 nucleus Neutron James Chadwick Nucleus Neutral 1.67492 x 10-27 kg 1.008 gm Neutral 8x 1012 kg/m3 electron 0-10 m proton (neutron) quark atom — 10-14m — 10-10 m — 10-15m
  8. Dalton, 1808 First to describe atoms in a modem, scientific sense Doesn't explain elecmcity + Idea of "atoms" Thomson, 1897 Thomson's Plum Pudding Model — Doan't explain why some of Rutherford's a-particles bounced back + Protons & electmns Rutherford, 1911 Rutherford shot a-particles through gold foil; some bounced back! — Why don't ttE electrons energy and crash inb the nucleus? + the Nucleus Bohr, 1913 Basis for our modern atomic model — Doesn't explain quantum mechanics + Bectron Shells Schrödinger, 1926 QuanüJtn mechanics — Why are some atoms of the same element heavier? + Subshens + 'Shells' are actually 'orbitals' Chadwick, 1932 + Neutrons! S.K. Sir The I-lowne or Chennistry Nucleus Electron Atom Neutron Proton Chronological Improvement in Atomic Model [email protected]
  9. J J Thomson's Atomic Model- 1898 After the discovery of Electron & Proton, J. J. Thomson, in 1898, tried to explain the arrangement of electron and proton within the atom. He stated that atoms were divisible and that atoms were made up of subatomic particles that accounted for the known electrical nature of the atom. Since atoms were neutral, he assumed that atoms must also be composed of positively charged particles to balance the negatively charged particles. His model showed the atom as a diffuse ball of positive charge with negative particles dispersed throughout. J.J. Thomson's model is referred to as the "Plum-pudding" Model. The pudding is the positive charge and the raisins are the negatively charged electrons that are scattered throughout the positive material. This model can be compared to a chocolate chip cookie where the cake portion of the cookie is like the positive charge and the chips are like the negative particles. S.K. Sir The Ilonne of Chernistry "Plum-pudding" Model Thomson's Atomic Model Atom Model—watermelon Positive charge Electron [email protected]
  10. RUTHERFORD's ATOMIC MODEL Gold Foil Ex eriment a This experiment led to the most substantial discovery of the atom C] A beam of Alpha rays was directed against a thin gold foil (0.0004 cm thick) and a circular screen coated with Zinc Sulphide (ZnS) was placed on the other side of the foil. Observation: 99.9% Alpha particles passed un-deflected through the Gold Foil and caused illumination on screen. (A) Very few Alpha particels underwent small and strong deflection after passing the central part of atom. (B) A very few (1 in 20000) were deflected backwards through angle greater than 90 degrees. (Path-C Circular screen coated with ZnS Detector Beom of a porticbes Radioactive Souce S.K. Sir The Home of Chemistry S ome alpha Some alpha panicles bounce particles are Most cz paticles travel ttvough the foa undeflected 1 Some particles are deflected by smat 2 an a particle travels bock from the 3 The atom is back. empty space ath C The is positively charged. os is the partic±e ath B ath A The nucleus carries roost Of atom's Gold atom defl ed. Most of an atom is a-npty space. Most alpha particles pass straight tl-xough foil. Nucleus of gol d atom Enlarged Cross Sectional Gold Foil [email protected]
  11. Rutherford's Atomic Model The atom is mostly empty space. Determined by the fact that most alp ha particles passed straight through t he foil un-deflected. The nucleus is small, and has a positi ve charge. Determined by the fact that only a sm all amount of alpha particles were de flected when they came close to the positive nucleus. Central portion of the atom is compact and dense. Determined by the fact that a very few Alpha particles came almost straight back towards source. Beam of a- very O 3 o 4 Rays Metallic Atom Foil Majority of a- Rays N cleus o a S.K. Sir Few An Atom of Gold O e Limitations of Rutherford's Atomic Model The Ilonne of Chemistry [email protected] An electron accelerating around the nucleus would continuously emit electromagnetic radiation and lose energy Therefore, it would eventually fall into the nucleus and the atom would collapse However, this is not consistent with real-world observations atoms are stable Fails to explain atomics ectra
  12. 'Orbits or shells or energy levels are the set circular paths where electrons moving with high speed around the nucleus. Stationary orbit describes the orbits. Every orbit has a predetermined amount of energy, and these circular orbits are referred to as Energy Levels. As long as the electrons in the fixed orbits continue to rotate around the nucleus, they will not emit energy. Orbits are represented as 1 ,2,3....or or El, E2, E3..... When electrons jump from one energy level to another, they change their energy. In an atom, electrons gain energy to go from a lower to a higher energy level. When an electron loses energy, however, it shifts from a higher to a lower energy level. Interpretation of Line Spectrum (various lines) in Hydrogen Spectrum. Electrons have both a known radius and orbit, i.e., known position and momentum at the same time [email protected] 18 8 S.K. Sir The Ilome or Chemistry I Energy Level Il Energy Level Ill Energy Level IV Energy Level Nucleus Energy IN When an electron jumps from inner orbit to outer orbit = Electron will gain energy And vice-versa
  13. Limitations: - It makes poor spectral predictions for larger atoms. It is accurate only with H-atom. It fails to explain fine lines of spectral lines and relative strength of spectral lines. As per The Heisenberg Uncertainty Principle it is impossible to known position and momentum of an electron at the same time. When the spectral line is broken into numerous components in the applied magnetic field, it fails to explain the Zeeman phenomenon. When the spectral line is divided up into fine lines in the presence of an electric field, it fails to describe the Stark effect. It also fails to explain cause of chemical combination and shape of molecules. Electrons move around the nucleus in three dimensional space and not in lane Limitations BOHR' Atomic Model STRUCTURE OF NUCLEUS nucleus Electron(-) proton (+) I - 10-15 m Oibtt 10 neutron (O) The diameter of the nucleus is about 10-5 times smaller than the diameter of the atom. [email protected] Discovery Of Neutron Rutherford in 1920 suggested that, an electron and proton might be so closely combined as to form a neutral particle which is given the name neutron. All the methods used for detection of P or e depend on the deflection of the charged particle by M.F or E.F. So, it is difficult to detect the no. Chadwick in 1932 demonstrated the existence of neutrons. This discovery led to presently accepted idea that the nucleus is built of protons and neutrons. I-le4+ Be9 —i + Chadwick detected the neutrons, since these particles, unlike protons, prodtlce no tracks in the cloud chamber and no ionization in the ionization chamber. These properties + the penetrating power of these particles show that the charge of these particles must be zero, and was identified as Rutherford's neutron. S.K. Sir The Ilonue of Chennistu•y
  14. Mass Number and Atomic Number Mass Number= No of Neutron + No of Proton Z=6 =Z+n 37Li Isotopes of Carbon 12 C 6 Element Symbol Atomic Number = No of Proton= No of electron Carbon•12 6 Protons 6 Neutrons Mass no: 6+6: 12 146 c Carbon•13 6 Protons 7 Neutrons Mass Different mass numbers Same atomic number Carbon-14 6 Protons 8 Neutrons Mass no : 6+8: 14 Protium o 1 1 Deuterium Unstable Tritium 3 Isotopes of Hydrogen Isotopes Atoms from the same element having same atomic number but different mass number. Stable S.K. Sir [email protected] The Ilonne of Chemistry
  15. > Any of two or more species of atoms or nuclei that have the same number of neutrons. Example: - As (A-77 & Z-33) & se (A-78 & Z-34) Both the atoms have 44 Neutrons S.K. Sir The Ilonue of Chennistry Atoms of different elements which posseses the same difference in the number of neutrons and protons. Example: - U (A-238 & Z-92) Th (A-234 & Z-90) [email protected] *Isobars are atoms of different elements with different atomic numbers but have the same mass number. *Electronic configurations of isobars differ. *Examples of isobars Argon (A-40 & Z-18), Potassium (A-40 & Z-1 9), and Calcium (A-40 & Z-20). Isotone Isodiapher Isobar Isoster CIAny of a group of molecules or ions that have the same number of valence electrons and have chemical or physical similarities. OFor example, SH, NH2 and CH3 are isosters of OH.
  16. Average Atomic Mass of an Element having Isotope: Once we collect the relative masses of each isotope from Mass Spectrometry data, we can use this information to calculate the average atomic mass(weight) of all atoms of an element taking into account the mass of each isotope present and the percent abundance for each isotope. This can be done through the following formula: Average Atomic Mass = (Mass of Isotope 1 x Fractional Abundance of Isotope 1) + (Mass of Isotope 2 x Fractional Abundance of Isotope 2) + Example-2: - The fractional abundance of C135 in a sample of chlorine containing only Cl-35 (atomic weight =34.9) and Cl-37 (atomic weight =36.9) isotopes, is 0.6. The average mass number of chlorine is Solution: - a-35 / 0-37 = (1-0.6) / 0.6=0.4 / 0.6 Average atomic mass = 34.9xO.6+36.9xO.4 = 35.7 am U Example-3: - Calculate the average atomic mass Of chlorine if its abundance in nature is 75.77% 35Cl, and 24.23% 37Cl. Average Atomic Mass Calculation alculate the avg. atomic mass of oxygen if its a undance in nature is 99.76%160, 0.04% 170, and 0.20% 180. Avg. Atomic = Mass 100 16.00 amu S.K. Sir The Ilonne of Chennistry Avg. Atornic Mass 100 35.48 arnu [email protected]
  17. D Cl All matter contains charged particles that are always moving; therefore, all objects emit EM waves. The wavelengths become shorter as the temperature of the material increases. C] EM waves carry radiant energy. Wavelength= distance from crest to crest. Frequency= number of wavelengths that pass a given point in 1 s. As frequency increases, wavelength becomes smaller. Cl In 1887, Heinrich Hertz discovered that shining light on a metal caused electrons to be ejected. Whether or not electrons were ejected depended upon frequency not the amplitude of the light. Remember energy depends on amplitude. C] Albert Einstein explained Hertz's discovery: EM waves can behave as a particle called a photon whose energy depends on the frequency of the waves. Velocity: Distance travelled by a wave in one second. Wavelength: Height of Crest or depth of through of a wave. [email protected] Electromagnetic Wave Magnetic field O Electric field S.K. Sir The I-Iome of Chemistry
  18. S. No 1 2 3 4 5 6 S. No 1 2 3 Electromagnetic Waves They have electric and magnetic fields associated with them. These fields and direction of propagation of wave are perpendicular to each other. They can pass through Vacuum. All Electromagnetic Waves travel with same velocity i.e, 299 792 458 m s They have physical significance as their wavelength are easily observed. They are actually emitted by the source. They have larger wavelength and represented by = c I v Particle It is localized in space Two particles can not occupy the same position in space at the same time. If there are two or particles in any region of space, the different particles do not interfere with each other and their sum is equal to the sum of individual particles. Matter Waves Electric and magnetic fields are not associated S.K. Sir with these waves. T Ine I-loune or Cluernistr•y They can not pass through Vacuum. They are associated with different particle and hence have different velocity but less than the velocity of light. Their wavelength is too small to observe and have no physical significance. They are associated with particle and hence not emitted by the source. They have shorter wavelength and represented by = h I mv Wave It is delocalized (spread out) in space Two or more waves can exist in the same region of space. When two waves present together, they interfere with each other i.e, the resultant wave can be larger or smaller than the individual wave. [email protected]
  19. [email protected] It is produced when hydrogen gas is taken in the discharge tube and the light emitted on passing electric discharge at low pressure is examined with a spectroscope. C] It is found to consist of a large number of lines that are grouped into different series. The names of different series are the Lyman series, Balmer series, Paschen series, Brackett series, and Pfund series. The emission spectrum is similar except that in place of dark lines, there are colored lines with dark space in between. C) Although a large number of lines are present in the hydrogen spectrum, Rydberg in 1890 gave a very simple theoretical equation for the calculation of the wavelength of these lines. The equation gives the calculation of the wave number (v — ) of the lines by the formula: 1 The limiting line of any spectral series in the hydrogen spectrum is the line when n2 in the Rydberg's formula is infinity, i.e. n2= 00. Emission spectrum is obtained when the radiation fromthe source IS directly analyzed in the spectroscope. Absorption spectrum is obtained when the white light if first passed thro Rydberg's substance and the transmitted light is analyzed in the spectroscope. The Hydrogen Formula spectrum is an emission spectrum because the colored lines are separated by dark spaces, but the absorptio has dark lines. Name of Series Lyman Balmer Paschen Bracket "fund The Home of Chemistry Discovery Year 1915 1885 1896 1922 1925 Region Ultra- Violet Visible I nfra-Red I nfra-Red I nfra-Red Electron Jumping to Electron Jumping From n = 5,6,7.....
  20. I I Il - upper Rydberg Equation n=5 n=2 n=l I I I I I Ill Pfund Series Brackett Series Paschen Series Visible [email protected] Balmer Series Visible Lyman Series No of lines in spectrum = n (n Where n= outermost orbit Y rogen Spectrum Emission Series S.K. Sir The I-loune or Chernistry
  21. S. No 1 2 Emission Spectrum It is produced by analyzing the radiant energy emitted by an excited substance. Absorption Spectrum It is produced when while light is passed through a substance and transmitted light is analyzed by a spectrograph. It consists of some bright lines separated by It consists of dark lines in otherwise continuous dark spaces. Increased Wavelength Absorption Spectrum Emission Spectrum [email protected] spectrum. Bohr Radius Expression 2 TTL z e Radius, E 11 ergy, — 13.6 X (Z2/n2) e V or E Velocity, v = ( h/ 2 acryl 231 —xne4 AE = S.K. Sir The I-Ionne or Chennistry -R H x (Z2/n2) 1 1 11
  22. de-Bro lie E uation C] The de Broglie wavelength is the wavelength, X, associated with a object and is related to its momentum and mass. C] Introduction: In 1923, Louis de Broglie, a French physicist, proposed a hypothesis to explain the theory of the atomic structure. By using a series of substitution de Broglie hypothesizes particles to hold properties of waves. Within a few years, de Broglie's hypothesis was tested by scientists shooting electrons and rays of lights through slits. What scientists discovered was the electron stream acted the same was as light proving de Broglie correct. C] All material particles in motion possesses wave character. C] The Angular momentum (mvr) of the electron should be an integral multiple of h 1 2 Tr. In other words, the angular momentum is quantized. This is the same as Bohr's condition for quantization of angular momentum of fixed energy orbits. moc2 In terms of Kinetic Energy Consider a particle of mass m moving with a velocity v Kinetic Energy of the particle The de Relation •The de Broglie Equation relates the wavelength of a particle to its momentum. Wavelength Planck's constant 6.626X10-34 J•s m Mass, kg Velocity, m/s 112 de Broglie Frequency mo = rest mass h = Planck's Constant h m = mass, R = Radius C = speed of light S.K. Sir The Ilome of Chemistry 2 2m 2m de Broglie wavelength 2m 2mE de Broglie wavelength in terms of KE [email protected]
  23. QElectromagnetic radiation is a form of energy that is produced by oscillating electric and magnetic disturbance, or by the movement of electrically charged particles traveling through a vacuum or matter. The electric and magnetic fields come at right angles to each other and combined wave moves perpendicular to both magnetic and electric oscillating fields thus the disturbance. Electron radiation is released as photons, which are bundles of light energy that travel at the speed of light as quantized harmonic waves. This energy is then grouped into categories based on its wavelength into the electromagnetic spectrum. These electric and magnetic waves travel perpendicular to each other and have certain characteristics, including amplitude, wavelength, and frequency. QElectromagnetic Spectrum: The arrangement obtained by arranging different types of electromagnetic S.K. Sir radiations in the decreasing or increasing order of their wavelengths or frequencies. Electromagnetic Spectrum: nm .001 nm 1 nm 10 nm Cosmic Gannn x-Rays UV Visible Rays Rays 24 390 Light .omlt .01 n 1 ft Micro- TV Radio 88 MHz 3100 mi Eledric Pover 60 Hz 750 446 542 578 Increasing order of Wavelength (X) wavelength 1 km 10m 10 cm 1 mm Visible 10 pm region 0.1 pm Inm IO•II m 10•13 m Radio waves Microwave & Infrared Ultraviolet X rays Gamma rays The Home of (',hemistrv frequency 300 kHz 30 MHz 3 GHz 300 GHz 3x1013 1-Iz 3x1015 1-Iz 3x1017 biz 3x1019 Hz 3x1021 1-Iz
  24. QEIectromagnetic Radiation and Energy: The energy associated with a radiation could have any value from infinity small to infinity large. Electromagnetic theory successfully interprets some properties of electromagnetic radiations especially mode of propagation, colour and diffraction. However it could not explain: Black Body Radiation: The temperature of the body determines the wavelength of light emitted and the wavelength of emitted light decreases with increase in temperature. For example, when a black body is heated, its colour changes from red to yellow to white with rise in temperature. Electromagnetic wave theory could not explain it. According to it, Radiation of only one wavelength could be emitted by a hot body irrespective of its temperature and there should be only one colour. All incident radiation is absorbed Blackbody Radiator Emitted Radiation 4 3.5 3 2.5 1.5 1 0.5 Photoelectric Effect: When a light radiation of a suitable frequency called threshold frequency falls on a metal surface, the ejection of electrons from the metal takes place. The ejection of electrons from the metal surface by radiation of suitable frequency is called Photoelectric effect and ejected electrons are called 5000 25000 30000 10000 15000 20000 Wavelength 3 40000 45000 photoelectrons. 50000 [email protected] S.K. Sir The Ilonue of Chemistry
  25. Wave Mechanical Model of Atom (Schrodinger Wave Equation) C) Erwin Schrodinger (1927) considered the electrons as three dimensional wave in electric field of the positively charged nucleus. To describe the behavior of a particle in a field of force or the change of a physical quantity over time, He proposed a mathematical equation which describes the energy and position of an electron in space and time, taking into account the dual nature of electron inside an atom. C] Significance of . It is a wave function and the solution to the equation. Represents amplitude of wave and describes how this amplitude varies with distance and direction. The equation may have different value of "IV" but all values may not be significant. The significant values are called EIGEN. These functions give Total Energy of electron. Significance of (Y2 ... Second derivative with respect to Z ()y2 Dz2 Position Schrodinger wave Function h2 Total Energ m = Mass of the Electron V = Potential energy of Electron ( Ze2/r) h = Planck's Constant X, y & Z are Cartesian co-ordinates specifying direction and distance. For electron waves, it represents intensity of Electron at any point, i.e, it tells about the probability of finding an electron of specific energy at different region of space. + It leads the idea of Orbital. [email protected] S.K. Sir The Home of Chemistry
  26. Important features of Quantum Mechanical Model of Atom In atoms, the Energy of Electron is Quantized. Quantized electronic energy levels exist in atoms. These are the outcomes of the wave like properties of electron. C] As the exact position and velocity of electron in an atom cannot be determined simultaneously, the path of electron in an atom can never be determined. Due to this, one talks of probability of finding electrons at different points around the nucleus. C] The probability of finding an electron at a point in an atom is proportional to tv2 which is called probability density. The region where the value of I/J2 is maximum is the reason of maximum electron density. Here the probability of finding the electron is maximum. C] The orbital wave function can be represented as a product of two functions. Orbital Wave Function = Radial function X Angular function C] The radial function depends upon the distance ( r ) from the nucleus while angular momentum depends upon the direction represented by angles with respect to the different axis. C] As per this model, electrons do not exist as tiny points inside the atom but instead surround the nucleus in a form resembling a cloud. S.K. Sir 'Phe I-Io•ne of Cheunisl I z z d*2-y2 Sub-Level orbital Sub-level - p pz orbital py orbital All three p orbitals together [email protected]
  27. Quantum Numbers Shell/ Orbit/Energy Level 1 "n" 2 3 Quantum numbers are the Index Numbers which are used to specify the position, energy, orientation in space and magnetic moment of an electron. Thus quantum numbers are the complete address of electron Quantum Number Sub-shell -1 ml = orbitals: Humber grincipal angular mom. magnetic spin m agnetic -2 -1 -2-3 s Syrn bol n I p Values 0.1 -1.1-1. d Deter mne size and erergy level, For H. energy deperd only on n, (Shell) Deter mne 3D shape of orbitals: (Subshel I = 0.1 Spatial orientation of ortnal$. spin stde of electron Distance of the electron from nucleus Shape of the orbital z x Orientation of the orbital S.K. Sir The 11mne of Chemistry Orientation of the electron spin [email protected]
  28. Cl It is designated by "m". ( m I to +1 ) C] Under the insurance of external magnetic field, electrons in a sub-shell adjust themselves in different orientations which are called orbitals. Thus each sub-shell is composed of orbitals which are designated by a different value of m. It is designated by "l" and depends on n. I = O to (n-l). For M (n=3), & 2 It gives angular momentum of electron. It gives the energies of Sub-levels. S < p < d < f Azimuthal QN 2 s s 2 Spin 3. Magnetic (Orientation) 4. Spin 2. Azimuthal (Shape) Principal (shape) It is a measure of the intrinsic angular momentum of electron. This number is denoted as Ms where m stands for momentum and s stands for spin. The spin of a particle is a vector quantity that, in three dimensions, is calculated using the Pauli spin matrices. Perhaps the most important spin number is s=+-1/2s=+-1/2 which is the spin of the elementary particles that compose matter. If a particle has a spin of +1/2, it is considered to be a spin up particle, and vice versa. I = O s-subshell 1=2 => d-subshell I | p-subshell 1=3 f-subshell C] It tells about the energy level to which electron belongs. C] It is designated by "n" where n = 1 2 3 [email protected]
  29. Properties of Quantum Numbers S.K. Sir The I Iome of Chemistrv Sub-shell Designation No of Sub-shell in a Shell One C] Sign up: +1/2 Sign down: -1/2 Three Symbol Name principal angular momentum magnetic spin Four Values ±1/2 5s Role determines tir energy (size) contributes to angular dependence (shar) and to a lesser extent energy determines the orkntation in space describes the electron spin (magnetic moment) 2s Two 5f 5g Five [email protected]
  30. Quantum Number Anal sis [email protected] Shell Main Energy Energy Level Sub- level Orbital's (m) Total Orbital's (n2) Max electrons in Energy Sub- level -3, Max electrons in Main Energy Level (2n2) 32 S.K. Sir The I Iome of Chemistrv
  31. Two electrons occupy the same orbital together despite the repulsion of like charges because they have opposite spins. Opposite spins create magnetic fields which tends to cancel the effect of the electrostatic charges. The number of nodal planes in an Orbit of any Energy Level (n) = n — I - 1 Actual probility Distribution Curve Probability Density (V2) x Volume of the Region Reason for stability of Half filled or Full filled Orbital's: C] Exchange of Energy Symmetry Aufbau Principle The electrons are filled in various shells in order of their increasing energies. More the (n + I ) value of a sub-shell, more the energy content. Hence 4s will be filled first S.K. Sir The I Iome of Chemistrv Hund's Rule No electron pairing takes place in the orbital's with equivalent energy until each orbital in the given Sub-shell contains one electron and the spin of any unpaired electrons are parallel. [email protected]
  32. Is Orbital arrangement in He Planck's Constant ApAx > — \ 4Tt Uncertainty in momentum Uncertainty in position AX' . AP > _ h S.K. Sir The Ilon•e or Chemistry N s Spin s x 1 1 1 1 1 x 1 1 1 1 1 1 Heisenberg's Uncertainty Principle It is impossible to measure simultaneously both the position and momentum (or velocity) of a microscopic particle with absolute accuracy or certainty. Very small mass particle shows significant uncertainty whereas Macroscopic particle shows uncertainty negligible Pauli's Exclusion Principle ONO two electrons in an atom can have all the four Quantum Numbers alike. An orbital can not have more than two electrons. The sublevels contain orbital's Number of orbital in a sub-shell. s-1 , p-3 , d-5 & f-7. C] Maximum number of electrons in a shell: [email protected] Is
  33. 2/T2me4Z2 22 112112 I 2 Value for nth Orbit C] Radius of Orbit, = rl x n2 Energy of electron, = El/n2 Velocity of electron, = vl/n hv hc/ o h/mv h/p 2 n 4rme2 Magnetic Moment, n (n+2) [email protected] Unit Conversion IJ=I 107 ergs; 1 J = 1 V x 1 C; As Wtn.%h Velocity 2TTZe2/nh S.K. Sir The Ilome of Chemistry
  34. S. No 1 2 3 4 S. No 1 2 3 4 Column-A Mn2+ V2+ Zn2+ Column-A K- Shell L- Shell H-Atom Boron Atom in Ground State X-Factor from SCI( Sir Column-B Paramagnetic, Colored Compound S.K. Sir The Ilome of Chemistry Paramagnetic, Colored Compound, Magnetic Moment-2.82 BM Diamagnetic Diamagnetic Column-B Electron in Circular Orbit, Shell of Lowest Energy Electron in Circular Orbit & Electron in Elliptical Orbit Bohr Atomic Model Electron in Circular Orbit & Electron in Elliptical Orbit [email protected]
  35. s. No 1 2 3 4 S. No 1 2 3 4 Column-A Quantum Theory Uncertainty Principle Wave Particle Dualism Line Spectra of Hydrogen Column-B Ritz Planck Heisenberg Balmer, Rydberg & Ritz Column-A Column-C Ax. Ap > Or = h/ 4TT A = hip S.K. Sir The Ilonne of Chemistry 1.0973732 x 10' — RN = Rydberg constant = — n, k are integers — k>n (always) Wave nature of Radiation Photon Nature of Radiation Interaction of a Photon with an Electron, such that quantum energy is slightly equal to or greater than the binding energy of electron, is more likely to result in Interaction of a photon with an electron, such that photon energy is much greater than the binding energy of electron, is more likely to result in [email protected] — Understanding this equation theoretically was a hot topic in the early 20th Century Column-B Diffraction & Interference Photoelectric effect & Compton effect Photoelectric effect Compton effect
  36. S. No 1 2 3 4 S. No 1 2 3 4 Column-A Electron can not exist in the nucleus Column-B Uncertainty Principle Microscopic particles in motion are associated with de Broglie wave No medium is required for propagation Concept of orbit was replaced by Orbital Electromagnetic wave, Transverse wave Uncertainty Principle Column-A Radius of Electron Orbit Energy of Electron Energy of Sub-shell Orientation of Atomic Orbital [email protected] Column-B Principal Quantum Number (n) Principal Quantum Number (n) Principal Quantum Number (n) & Magnetic Quantum Number (m) Magnetic Quantum Number (m) S.K. Sir The I Iome of Chemistry
  37. S. No I 2 3 4 5 6 S. No 1 2 3 4 Column-A Aufbau Principle de Broglie Angular Momentum Hund's Rule Balmer Series Planck's Law Column-A Mg2+ Fe2+ C03+ Ca2+ Column-B Electronic Configuration h/mv = h/p mvr Orientation of electron S.K. Sir The Home or Chemistry Line spectrum in visible region Photon Column-B Zero spin multiplicity, Total spin=O Spin multiplicity = 3, Total spin=2 Spin multiplicity = 3, Total spin=2 Zero spin multiplicity, Total spin=O S. No 2 3 4 5 6 s. No 1 2 3 4 Column-A Thomson Pauli Becqerel Soddy Bohr Chadwick Column-A Is 3p [email protected] Column-B Cathode Rays Exclusion Principle Radioactivity Isotopes Atomic Model Neutron Column-B Radial Node-I Angular Node-O Radial Node-O Angular Node-O Radial Node-O Angular Node-I Radial Node-I Angular Node-I
  38. S.K. Sir The Ilome of Chemistry Thank You [email protected] What Next Periodic Classification

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