CHEM 101 Part 1 2021-2022 Lecture Notes PDF

Inorganic Chemistry 1 Inorganic Chemistry Group 2022-2023  (Lec. 01) 2 Inorganic Chemistry Group 2022-2023 History of the atom (Theories & Models) 3 Inorganic Chemistry Group 2022-2023 History of Atomic Theory History of Atomic Theory Greek Philo...

Inorganic Chemistry 1 Inorganic Chemistry Group 2022-2023  (Lec. 01) 2 Inorganic Chemistry Group 2022-2023 History of the atom (Theories & Models) 3 Inorganic Chemistry Group 2022-2023 History of Atomic Theory History of Atomic Theory Greek Philosophy thinking 4 Inorganic Chemistry Group 2022-2023 Who Discovered Atoms Democritus Idea (400 B.C.) Matter was made of tiny particles that couldn't be divided and called atoms. He had no experimental evidence to support A = no + tom = divide his thoughts. 5 Inorganic Chemistry Group 2022-2023 Who Discovered Atoms Aristotle’s idea Aristo didn't believe in the atomic theory. Matter was made of four elements, fire, dust, water and air in different proportions. Any matter can change to the other by changing FDWA proportions. e.g: Copper to Gold. 6 Inorganic Chemistry Group 2022-2023 History of Atomic Theory History of Atomic Theory Experimental thinking 7 Inorganic Chemistry Group 2022-2023  Dalton’s Atomic Theory Dalton had four major points (postulates) to his theory. 1. Elements is composed of tiny particles called atoms. 2. The atom is very minute indivisible solid particle. 3. Masses of atoms of the same element are similar but they differ from one element to another. 4. The compounds are formed by the combination of atoms of different elements in simple numerical ratios. John Dalton 8 Inorganic Chemistry Group 2022-2023  Discovery of the electron Electron was discovered by Joseph John Thomson in 1897 when he was studying the properties of cathode ray. J.J. Thomson 9 Inorganic Chemistry Group 2022-2023 Cathode ray Experiment Stream of invisible rays will be emitted from the cathode (- ve pole) causing a green fluorescent glow on hitting the tube wall. 10 Inorganic Chemistry Group 2022-2023 Cathode ray Experiment In presence of electric field, the behaviour of cathode rays is similar to that expected of negatively charged particles. 11 Inorganic Chemistry Group 2022-2023 Properties of cathode ray particle 1. Cathode rays travel in straight lines. 2. They are independent of the material of the cathode. 3. Cathode ray consists of negatively charged particles. 12 Inorganic Chemistry Group 2022-2023 Charge/Mass Ratio of Electron J. J. Thomson measured the relative charge-by- mass-ratio (e/m) of cathode ray particle using deflection in both electric and magnetic field. e/m= −1.76x108 coulomb per gram (C/g). 13 Inorganic Chemistry Group 2022-2023 14 Inorganic Chemistry Group 2022-2023 Millikan Oil Drop Experiment Charge (e) of electron. Robert Andrews Millikan 15 Inorganic Chemistry Group 2022-2023 Millikan Oil Drop Experiment 16 Inorganic Chemistry Group 2022-2023 17 Inorganic Chemistry Group 2022-2023 Millikan Oil Drop Experiment mg = Eq= qV/d E : the electric field between the plates = V/d V: the potential difference between plates d: the separation between plates. 18 Inorganic Chemistry Group 2022-2023 Charge of Electron Millikan found that all the charges were multiples of one basic charge namely 1.6×10−19 C 19 Inorganic Chemistry Group 2022-2023 Charge of Electron Charge of electron −1.6×10−19 Coulombs 20 Inorganic Chemistry Group 2022-2023 Mass of Electron J. J. Thomson measured the charge-by-mass- ratio (e/m) of cathode ray particle using deflection in both electric and magnetic field. e/m= −1.76x108 coulomb per gram (C/g). 21 Inorganic Chemistry Group 2022-2023 Mass of Electron J. J. Thomson measured the charge-by-mass- ratio (e/m) of cathode ray particle using deflection in both electric and magnetic field. e/m= −1.76×108 -1.6x10-19 (C)/ m = -1.76x108(C/g) m = -1.6x10-19 / - 1.76x108 = 9.11x10-28 g 22 Inorganic Chemistry Group 2022-2023 Anode Ray (Positive Ray) (Canal Ray) Since the atom is electrically neutral there must be positively charged particles present in the atom to neutralize the negative charges of the electrons. Eugen Goldstein experimentally proved the existence of protons in the atom. 23 Inorganic Chemistry Group 2022-2023 Canal (anode) Rays Eugen Goldstein Experiment 24 Inorganic Chemistry Group 2022-2023 Explanation of production of positive rays When very high voltage is applied, it ionises the gas and it is positive ions of gas that constitutes the canal ray. It is actually the nucleus or kernel of the gas that was used in the tube and hence it has properties different from the cathode rays which were made up of electrons. 25 Inorganic Chemistry Group 2022-2023 Properties of anode rays Travel in straight lines. Positively charged. q/m ratio for positive ray particles differ with different gases. The velocity of anode rays is much smaller than the velocity of cathode rays. 26 Inorganic Chemistry Group 2022-2023 The difference between Anode rays and Cathode rays? 27 Inorganic Chemistry Group 2022-2023 Thomson’s Atomic Model Atom is a solid sphere of uniform positive electric charges (pudding) in which a number of negatively charged electrons (plums) is embedded to make the atom electrically neutral. 28 Inorganic Chemistry Group 2022-2023  (Lec. 02) 29 Inorganic Chemistry Group 2022-2023 Rutherford’s Scattering Experiment Used the gold foil experiment to discover the nucleus. Shot high energy beam of alpha particles into gold foil. 30 Inorganic Chemistry Group 2022-2023 Rutherford’s Scattering Experiment 31 Inorganic Chemistry Group 2022-2023 Rutherford’s Scattering Experiment 32 Inorganic Chemistry Group 2022-2023 Rutherford Conclusions Observation Conclusion Most of the alpha particles The atom is mostly empty went through he concluded… space Few particles were deflected The alpha particle came close at small angles he to something small and concluded… positive (nucleus) Very rarely particles were The alpha particles hit a deflected at large angles he small, very dense, and concluded… positively charged center (nucleus) 33 Inorganic Chemistry Group 2022-2023 Rutherford Conclusions 1. Atom contains heavy and positively charged part at the center and called nucleus. 2. The nucleus occupy minute fraction of the total volume of atom. 3. Atom is not all solid. 4. Electrons are revolving around the nucleus in closed circular paths with fast speeds. 5. The number of negatively charged electrons dispersed outside the nucleus is same as number of positively charge in the nucleus. 6. It explains the overall electrical neutrality of an atom. 7. Rutherford proposed the planetary model of the atom. 34 Inorganic Chemistry Group 2022-2023 Planetary Model of Atom Atom is extremely small sized particle. It has a complicated structure which resembles the solar system, since it is composed of a central nucleus (sun) and the electrons revolve around it (the planets). 35 Inorganic Chemistry Group 2022-2023 Drawbacks of Rutherford’s Model 1- Rutherford's model could not explain the stability of the atom. The electron revolve in a circular motion, will loss energy and its speed will decrease and start to move in spiral path and finally will fall into the nucleus, which means the atom will be unstable. 2. Rutherford's model could not explain the radiation emitted from some atoms. 37 Inorganic Chemistry Group 2022-2023 Extra Mass Atoms of different elements have different numbers of protons giving their nuclei different charges.... If the protons were the only particles in the nucleus, then a helium nucleus would have two protons and therefore only twice the mass of hydrogen. 38 Inorganic Chemistry Group 2022-2023 Discovery of Neutrons (Chadwick Experiment) 4 9 12 + 1 2𝐻𝑒 + 4𝐵𝑒 6𝐶 + 0𝑛 39 Inorganic Chemistry Group 2022-2023 Chadwick’s observations and conclusions During an experiment it was found that, when alpha particles bombarded Beryllium nuclei, some radiations were observed. These radiations were found to be undevoted in an electric field. So, the earlier scientist thought these radiations could be electromagnetic radiation and hence discarded it. But Chadwick repeated the experiment and made the following observations. 40 Inorganic Chemistry Group 2022-2023 Chadwick’s observations and conclusions 1. A paddle wheel was placed behind the Beryllium nucleus and the nucleus was bombarded with α– particles. It was observed that the paddle wheel rotates. From this, it was concluded that the beryllium nucleus emits some invisible radiations having material particles. 2. When these invisible radiations were allowed to pass through an electric field, there was no deviation seen. This confirmed the fact that these rays contained neutral particles. These neutral particles were called neutrons by James Chadwick. 41 Inorganic Chemistry Group 2022-2023 Atomic Number and Mass Number 42 Inorganic Chemistry Group 2022-2023 Atomic Number and Mass Number 43 Inorganic Chemistry Group 2022-2023  Isotopes The isotopes are atoms of the same element contain the same number of protons and electrons but contain different numbers of neutrons in their nuclei. Same Atomic Number and Different Mass Number. 44 Inorganic Chemistry Group 2022-2023  Hydrogen Isotopes 45 Inorganic Chemistry Group 2022-2023  Carbon Isotopes 46 Inorganic Chemistry Group 2022-2023  Oxygen Isotopes 47 Inorganic Chemistry Group 2022-2023 48 Inorganic Chemistry Group 2022-2023 Atomic Mass (Weight) The atomic weight of an element is the relative mass of an average atom of the element expressed in atomic mass units. 49 Inorganic Chemistry Group 2022-2023 Atomic Mass (Weight ) Scale Average Atomic Mass (Weight ) of element based on the abundance (percentage) of each isotope of that element in nature. Average Atomic Mass(Weight ) of element = (Atomic mass of isotope 1 x its abundance as a decimal) + (Atomic mass of isotope 2 x its abundance as a decimal) + …..etc. 50 Inorganic Chemistry Group 2022-2023 Atomic Mass Unit (amu) Instead of grams, the unit we use is the Atomic Mass Unit (amu). One atomic mass unit is equal to 1/12 the mass of a carbon-12 atom (12C). Carbon-12 chosen because of its isotope purity. 1 amu = 1.66 x 10-24 g 51 Inorganic Chemistry Group 2022-2023 Atomic Mass (Weight ) of Chlorine (Cl) Isotope Abundance Atomic mass (amu) 35 17Cl 75.77 34.969 37 17Cl 24.23 36.966 Atomic mass of Cl = (34.969x 0.7577) + (36.969x 0.2423) = 35.45 amu 52 Inorganic Chemistry Group 2022-2023 Atomic Mass (Weight ) of Carbon (C) Isotope Atomic mass % abundance (Atomic mass ) x (abundance as a decimal) 𝟏𝟐 𝟔𝐂 12 98.89% 12 x 0.9889 =11.87 𝟏𝟑 13 1.11% 13 x 0.0111 = 0.14 𝟔𝐂 𝟏𝟒 𝟔𝐂 14 0.01% 14 x 0.0001 = 0.0014 Atomic Mass of C = 11.87 + 0.14 + 0.0014 =12.011 amu 53 Inorganic Chemistry Group 2022-2023