Chem 015 Topic 1 Intro PDF

CHEM 015 TOPIC 1: REVIEW OF ATOMIC CONCEPTS & THEORIES DR. GLORINA P. OROZCO  TOPIC OUTLINE Part 1: Review of Atomic CONCEPTS A. Intro: Chemistry Applications B. Atomic Theories C. Ions & Compounds Part 2: Quantum Theory and the Electronic Structure of Atoms  Chemis...

CHEM 015 TOPIC 1: REVIEW OF ATOMIC CONCEPTS & THEORIES DR. GLORINA P. OROZCO  TOPIC OUTLINE Part 1: Review of Atomic CONCEPTS A. Intro: Chemistry Applications B. Atomic Theories C. Ions & Compounds Part 2: Quantum Theory and the Electronic Structure of Atoms  Chemistry: A Science for the 21st Century Health and Medicine Sanitation systems Surgery with anesthesia VACCINES Antibiotics Gene therapy Energy and the Environment Fossil fuels Solar energy Nuclear energy 3  Chemistry: A Science for the 21st Century ❖ Materials and Technology Polymers, ceramics, liquid crystals Room-temperature superconductors Molecular computing ❖ Food and Agriculture Genetically Modified crops (GMOs) Bio pesticides (eg. Bacillus thuringensis) Organic fertilizers 4 Atomic Theories, Ions & Compounds PART I Dalton’s Atomic Theory Law of Multiple Proportions 6 16 X + 8Y 8 X2Y Law of Conservation of Mass 7 Cathode Ray Tube J.J. Thomson, measured mass/charge of e- (1906 Nobel Prize in Physics) 8 Cathode Ray Tube 9  Millikan’s Experiment Measured mass of e- (1923 Nobel Prize in Physics) e- charge = -1.60 x 10-19 C Thomson’s charge/mass of e- = -1.76 x 108 C/g e- mass = 9.10 x 10-28 g 10 Types of Radioactivity (uranium compound) 11 Thomson’s Model 12  Rutherford’s Experiment (1908 Nobel Prize in Chemistry)  particle velocity ~ 1.4 x 107 m/s (~5% speed of light) 1. atoms positive charge is concentrated in the nucleus 2. proton (p) has opposite (+) charge of electron (-) 3. mass of p is 1840 x mass of e- (1.67 x 10-24 g) 13  Rutherford’s Model of the Atom atomic radius ~ 100 pm = 1 x 10-10 m nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m “If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.” 14 Chadwick’s Experiment (1932) (1935 Noble Prize in Physics) H atoms - 1 p; He atoms - 2 p mass He/mass H should = 2 measured mass He/mass H = 4  + 9Be 1n + 12C + energy neutron (n) is neutral (charge = 0) n mass ~ p mass = 1.67 x 10-24 g 15 mass p ≈ mass n ≈ 1840 x mass e- 16  Atomic number, Mass number and Isotopes Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei Mass Number A ZX Element Symbol Atomic Number 1 2 3 1H 1H (D) 1H (T) 235 238 92 U 92 U 17  The Isotopes of Hydrogen (1) Protium (2) Deuterium (3) Tritium 18  14 How many protons, neutrons, and electrons are in 6 C ? 6 protons, 8 (14 - 6) neutrons, 6 electrons 11 How many protons, neutrons, and electrons are in 6 C ? 6 protons, 5 (11 - 6) neutrons, 6 electrons 19  Noble Gas 20 Halogen The Modern Periodic Table Group Period Alkali Earth Metal Alkali Metal  Chemistry In Action Natural abundance of elements in Earth’s crust Natural abundance of elements in human body 21 A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces H2 H2O NH3 CH4 A diatomic molecule contains only two atoms H2, N2, O2, Br2, HCl, CO diatomic elements A polyatomic molecule contains more than two atoms O3, H2O, NH3, CH4 22 An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. 11 protons 11 protons Na 11 electrons Na+ 10 electrons anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. 17 protons 17 protons Cl 17 electrons Cl- 18 electrons 23 A monatomic ion contains only one atom Na+, Cl-, Ca2+, O2-, Al3+, N3- A polyatomic ion contains more than one atom OH-, CN-, NH4+, NO3- 24 Common Ions Shown on the Periodic Table 25  27 3+ How many protons and electrons are in 13 Al ? 13 protons, 10 (13 – 3) electrons 78 2- How many protons and electrons are in 34 Se ? 34 protons, 36 (34 + 2) electrons 26 Formulas and Models 27 A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance An empirical formula shows the simplest whole-number ratio of the atoms in a substance molecular empirical H2O H2O C6H12O6 CH2O O3 O N2H4 NH2 28 ionic compounds consist of a combination of cations and an anions The formula is usually the same as the empirical formula The sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero The ionic compound NaCl 29 The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds. 30 Formula of Ionic Compounds 2 x +3 = +6 3 x -2 = -6 Al2O3 Al3+ O2- 1 x +2 = +2 2 x -1 = -2 CaBr2 Ca2+ Br- 1 x +2 = +2 1 x -2 = -2 Na2CO3 Na+ CO32- 31 Chemical Nomenclature Ionic Compounds ◦ Often a metal + nonmetal ◦ Anion (nonmetal), add “ide” to element name BaCl2 barium chloride K2O potassium oxide Mg(OH)2 magnesium hydroxide KNO3 potassium nitrate 32  Transition metal ionic compounds ◦ indicate charge on metal with Roman numerals FeCl2 2 Cl- -2 so Fe is +2 iron(II) chloride FeCl3 3 Cl- -3 so Fe is +3 iron(III) chloride Cr2S3 3 S-2 -6 so Cr is +3 (6/2) chromium(III) sulfide 33 34 35 Molecular compounds −Nonmetals or nonmetals + metalloids −Common names − H2O, NH3, CH4, −Element furthest to the left in a period and closest to the bottom of a group on periodic table is placed first in formula −If more than one compound can be formed from the same elements, use prefixes to indicate number of each kind of atom −Last element name ends in ide 36  Molecular Compounds HI hydrogen iodide NF3 nitrogen trifluoride SO2 sulfur dioxide N2Cl4 dinitrogen tetrachloride NO2 nitrogen dioxide N2O dinitrogen monoxide 37 38 An acid can be defined as a substance that yields hydrogen ions (H+) when dissolved in water. For example: HCl gas and HCl in water Pure substance, hydrogen chloride Dissolved in water (H3O+ and Cl−), hydrochloric acid 39 40 An oxoacid is an acid that contains hydrogen, oxygen, and another element. HNO3 nitric acid H2CO3 carbonic acid H3PO4 phosphoric acid 41 Naming Oxoacids and Oxoanions 42 The rules for naming oxoanions, anions of oxoacids, are as follows: 1. When all the H ions are removed from the “- ic” acid, the anion’s name ends with “-ate.” 2. When all the H ions are removed from the “- ous” acid, the anion’s name ends with “-ite.” 3. The names of anions in which one or more but not all the hydrogen ions have been removed must indicate the number of H ions present. For example: ◦ H2PO4- dihydrogen phosphate ◦ HPO4 2- hydrogen phosphate ◦ PO43- phosphate 43 44 A base can be defined as a substance that yields hydroxide ions (OH-) when dissolved in water. NaOH sodium hydroxide KOH potassium hydroxide Ba(OH)2 barium hydroxide 45  Hydrates are compounds that have a specific number of water molecules attached to them. BaCl2 2H2O barium chloride dihydrate LiCl H2O lithium chloride monohydrate MgSO4 7H2O magnesium sulfate heptahydrate Sr(NO3)2 4H2O strontium nitrate tetrahydrate CuSO4 5H2O CuSO4 46 47 Organic chemistry is the branch of chemistry that deals with carbon compounds Functional Groups H H H O H C OH H C NH2 H C C OH H H H methanol methylamine acetic acid 48 49  Quantum Theory and the Electronic Structure of Atoms PART II  Properties of Waves Wavelength (l) is the distance between identical points on successive waves. Amplitude is the vertical distance from the midline of a wave to the peak or trough. Frequency (n) is the number of waves that pass through a particular point in 1 second (Hz = 1 cycle/s). The speed (u) of the wave = l x n 51 Maxwell (1873), proposed that visible light consists of electromagnetic waves. Electromagnetic radiation is the emission and transmission of energy in the form of electromagnetic waves. Speed of light (c) in vacuum = 3.00 x 108 m/s All electromagnetic radiation lxn=c 52 53 A photon has a frequency of 6.0 x 104 Hz. Convert this frequency into wavelength (nm). Does this frequency fall in the visible region? l lxn=c l = c/n n l = 3.00 x 108 m/s / 6.0 x 104 Hz l = 5.0 x 103 m l = 5.0 x 1012 nm 54 Mystery #1, “Heated Solids Problem” Solved by Planck in 1900 When solids are heated, they emit electromagnetic radiation over a wide range of wavelengths. Radiant energy emitted by an object at a certain temperature depends on its wavelength. Energy (light) is emitted or absorbed in discrete units (quantum). E=hxn Planck’s constant (h) h = 6.63 x 10-34 J s 55 Mystery #2, “Photoelectric Effect” hn Solved by Einstein in 1905 Light has both: KE e- 1. wave nature 2. particle nature Photon is a “particle” of light hn = KE + W KE = hn - W where W is the work function and depends how strongly electrons are held in the metal 56 When copper is bombarded with high-energy electrons, X rays are emitted. Calculate the energy (in joules) associated with the photons if the wavelength of the X rays is 0.154 nm. E=hxn E=hxc/l E = 6.63 x 10-34 (J s) x 3.00 x 10 8 (m/s) / 0.154 x 10-9 (m) E = 1.29 x 10 -15 J 57 Line Emission Spectrum of Hydrogen Atoms 58 59  Bohr’s Model of the Atom (1913) 1. e- can only have specific (quantized) energy values 2. light is emitted as e- moves from one energy level to a lower energy level 1 En = -RH ( ) n2 n (principal quantum number) = 1,2,3,… RH (Rydberg constant) = 2.18 x 10-18J 60  E = hn E = hn 61 Why is e- energy quantized? De Broglie (1924) reasoned that e- is both particle and wave. h 2pr = nl l = mu u = velocity of e- m = mass of e- 62  Chemistry in Action: Laser – The Splendid Light Light Amplification by the Stimulated Emission of Radiation Laser light is (1) intense, (2) monoenergetic, and (3) coherent 63  Chemistry in Action: Electron Microscopy le = 0.004 nm STM image of iron atoms on copper surface Electron micrograph of a normal red blood cell and a sickled red blood cell from the same person 64  Schrodinger Wave Equation In 1926 Schrodinger wrote an equation that described both the particle and wave nature of the e- Wave function (y) describes: 1. energy of e- with a given y 2. probability of finding e- in a volume of space Schrodinger’s equation can only be solved exactly for the hydrogen atom. Must approximate its solution for multi-electron systems. 65  Schrodinger Wave Equation y is a function of four numbers called quantum numbers (n, l, ml, ms) principal quantum number n n = 1, 2, 3, 4, …. distance of e- from the nucleus n=1 n=2 n=3 Where 90% of the e- density is found for the 1s orbital 67  QUANTUM NUMBERS The electrons in the different sublevels can be best described by sets of 4 quantum numbers: 1. The Principal Quantum number (n) – gives the number of the main energy level where the electron revolves. 2. The Secondary or Azimuthal Quantum number (l) – measures the angular momentum of the electron. It also indicates the number of sublevels in each energy level where the values can range from 0 to n-1. 3. The Magnetic Quantum number (m) - refers to the behavior of an electron in a magnetic field with assigned values from 0 to 1. 4. The Spin Quantum number (s) – describes the spin of the electron about its axis. The values are (-1/2) for clockwise spinning (↓) and (+1/2) for counterclockwise spinning (↑). 68  Values of Quantum Numbers Principal Azimuthal Magnetic (m) Spin (s) (n) (l) 1 0 =s 0 -½ ½ 2 0 =s 0 -½ ½ 1=p -1 0 1 -½ ½ -½ ½ -½ ½ 3 0 =s 0 -½ ½ 1=p -1 0 1 -½ ½ -½ ½ -½ ½ 2=d -2 -1 0 1 2 -½ ½ -½ ½ -½ ½ -½ ½ -½ ½ 4 0 =s 0 -½ ½ 1=p -1 0 1 -½ ½ -½ ½ -½ ½ 2=d -2 -1 0 1 2 -½ ½ -½ ½ -½ ½ -½ ½ -½ ½ 3=f -3 -2 -1 0 1 2 3 -½ ½ -½ ½ -½ ½ -½ ½ -½ ½ -½ ½ -½ ½  Schrodinger Wave Equation quantum numbers: (n, l, ml, ms) angular momentum quantum number l for a given value of n, l = 0, 1, 2, 3, … n-1 l=0 s orbital n = 1, l = 0 l=1 p orbital n = 2, l = 0 or 1 l=2 d orbital n = 3, l = 0, 1, or 2 l=3 f orbital Shape of the “volume” of space that the e- occupies 70 l = 0 (s orbitals) l = 1 (p orbitals) 71 ml = -1, 0, or 1 3 orientations is space 72 Schrodinger Wave Equation quantum numbers: (n, l, ml, ms) magnetic quantum number ml for a given value of l ml = -l, …., 0, …. +l if l = 1 (p orbital), ml = -1, 0, or 1 if l = 2 (d orbital), ml = -2, -1, 0, 1, or 2 orientation of the orbital in space 73 l = 2 (d orbitals) 74 ml = -2, -1, 0, 1, or 2 5 orientations is space 75  Schrodinger Wave Equation (n, l, ml, ms) spin quantum number ms ms = +½ or -½ ms = +½ ms = -½ 76  Schrodinger Wave Equation quantum numbers: (n, l, ml, ms) Existence (and energy) of electron in atom is described by its unique wave function y. Pauli exclusion principle - no two electrons in an atom can have the same four quantum numbers. Each seat is uniquely identified (E, R12, S8) Each seat can hold only one individual at a time 77  Principles of Filling-Up Orbitals 1. Pauli’s Exclusion Principle states that no more than 2 electrons can occupy a single orbital. 2. Aufbau’s Rule In distributing electrons, the lowest energy levels are filled to the capacity before going to the next level. 3. Hund’s Rule Specifies that within a given sublevel, one electron is placed in each orbital before pairing could occur. 78  Principles of Filling-Up Orbitals The order of filling orbitals has been established by experiments, principally through spectroscopy and magnetic studies. It is in this order that should be followed in assigning electron configurations to the elements. Except for a few elements, the order in which orbitals are filled is: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 79  Order of orbitals (filling) in multi-electron atom 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s 80 81  Schrodinger Wave Equation quantum numbers: (n, l, ml, ms) Shell – electrons with the same value of n Subshell – electrons with the same values of n and l Orbital – electrons with the same values of n, l, and ml How many electrons can an orbital hold? If n, l, and ml are fixed, then ms = ½ or - ½ y = (n, l, ml, ½) or y = (n, l, ml, -½) An orbital can hold 2 electrons 82 How many 2p orbitals are there in an atom? n=2 If l = 1, then ml = -1, 0, or +1 2p 3 orbitals l=1 How many electrons can be placed in the 3d subshell? n=3 If l = 2, then ml = -2, -1, 0, +1, or +2 3d 5 orbitals which can hold a total of 10 e- l=2 83  Energy of orbitals in a single electron atom Energy only depends on principal quantum number n n=3 n=2 1 En = -RH ( ) n2 n=1 84 Electron configuration is how the electrons are distributed among the various atomic orbitals in an atom in principal shells & subshells. number of electrons in the orbital or subshell 1s1 principal quantum angular momentum number n quantum number l Orbital diagram H 1s1 85  Paramagnetic Diamagnetic unpaired electrons all electrons paired 2p 2p 86 Electron configuration The space around the nucleus is divided into shells or main energy levels and subshells or sublevels. Main Energy Level The energy levels or shells increase in energy as the distance from the nucleus increases. The energy levels are designated either by letters starting with K (or with numbers). The closest to the nucleus is K. The maximum number of electrons in each energy level is equal to 2n2 where n is the number of the energy level. 87 The Sublevels The energy levels are further subdivided into sublevels designated by the letters s, p, d, f, g the number of which corresponds to the number of the energy level. Each sublevel has a set of orbitals which are of equal energy (degenerate). The orbital is the region in space around the nucleus where the probability of finding the electron is greatest. 88 What is the electron configuration of Mg? Mg 12 electrons 1s < 2s < 2p < 3s < 3p < 4s 1s22s22p63s2 2 + 2 + 6 + 2 = 12 electrons Abbreviated as [Ne]3s2 [Ne] 1s22s22p6 What are the possible quantum numbers for the last (outermost) electron in Cl? Cl 17 electrons 1s < 2s < 2p < 3s < 3p < 4s 1s22s22p63s23p5 2 + 2 + 6 + 2 + 5 = 17 electrons Last electron added to 3p orbital n = 3 l = 1 ml = -1, 0, or +1 ms = ½ or -½ Outermost subshell being filled with electrons 90  REFERENCES: o Baruch, 2020. Chemistry: Laboratory Instructions & Exercises https://www.baruch.cuny.edu/wsas/academics/natural_science/Che mistry1000LaboratoryNotes.htm o Muniratu, Maliki. 2019. Introductory Chemistry I. Edo University. https://www.edouniversity.edu.ng/oer/lecturenotes/chm_111_introdu ctory_chemistry_i_lecture_notes_20182019 o Roussel, Marc. 2020. General Chemistry http://people.uleth.ca/~roussel/C1000/ http://www.bvrit.ac.in/Freshman_Lab_Manuals/freshman_engineering _chemistry/Engineering%20Chemistry.pdfwww.worldofteaching.com http://www.worldofteaching.com  Thank You! Be ready for a quiz next meeting