Atoms and Atomic Structure Lesson 2 PDF

LESSON2: ATOMS AND ATOMIC STRUCTURE By: giermin sahagun GOALS FOR THE DAY HISTORY OF ATOMIC STRUCTURE ATOMIC STUCTURE ATOMIC MASS AND ATOMIC NUMBER ISOTOPE, ISOBAR ,ISOTONE AND ISOMER RELATIVE ATOMIC MASS ELECTRIC CONFIGURATION  J. J. Thomson Ernest Rutherford Jame...

LESSON2: ATOMS AND ATOMIC STRUCTURE By: giermin sahagun GOALS FOR THE DAY HISTORY OF ATOMIC STRUCTURE ATOMIC STUCTURE ATOMIC MASS AND ATOMIC NUMBER ISOTOPE, ISOBAR ,ISOTONE AND ISOMER RELATIVE ATOMIC MASS ELECTRIC CONFIGURATION  J. J. Thomson Ernest Rutherford James Chadwick Discover electron in Discover Proton in Discover Neutron in 1897 1919 1932 ◦Michael Faraday ◦Showed that chemical reactions occur when electricity is passed through certain chemical solutions. ◦His findings gave the 1st hint that atom is still contained smaller particels ◦William Crookes ◦ Showed that if high voltage is passed through the gas discharged tube, cathode rays move from the negative electrode (cathode) to the positive electrode ( anode) ◦Roentgen discovered X-ray ◦ Eugen Goldstein ◦ Date = 1886 ◦ Discovery = ◦ Discovered protons using cathode ray tube. Rays were observed traveling in the direction opposite of the cathode rays. ◦ Protons are positive ◦ Importance = ◦ Atoms have both negative and positive particles Particle Symbol Mass (u) Charge Electron e 0.00055 -1 Proton p 1.0073 +1 Neutron n 1.0087 0 ATOMIC MASS More problem 1. How many neutrons, protons and electrons are in the nucleus of the following elements : ELEMENT NAME Atomic Atomic Number of Number of Number of Mass Number Proton electron neutron Sodium (Na) 23 11 Xenon (Xe) 131 54 Tungsten (W) 184 74 Hydrogen (H) 1 0 Cobalt (Co) 27 14 Isobar , isotope and isomers Isobar , isotope and isomers  Isobar , isotope and isotone and and and and Relative atomic mass ◦ The average value for the isotopes of the element. ◦ It takes into account the percentage abundance of the isotopes. Relative atomic mass Mass spectromete r ◦ Itused to determine the types of isotopes present, the exact masses of these isotopes and the relative amount of each isotope present in an element  Electric Configuration and Four Quantum Numbers ◦The space around the nucleus is divided into shells or main energy levels and subshells or sublevels  Quantum Numbers Summary Name Symbol Allowed Property Values Principal N Positive Orbital size integers and energy level Secondary l Integers from Orbital shape (0 to (n-1) (sublevels/ subshells) Magnetic Integers –l to Orbital +l Orientation Spin +1/2 or -1/2 Electron spin direction Main energy level ◦ What is the maximum number of electron can allowed in a single energy level ◦ A) first level – n=1 b) 3rd level – n= 3 Sublevel shell ◦ Determine the shape of  Shape of the orbital ◦ S= spherical shape p= dumbbell shape ◦ d= fourlobe shape  Magnetic quantum number ◦The magnetic quantum number is an integer that specifies the orientation of the orbital  Magnetic quantum number ◦ It splits the sub-shells (such as s,p,d,f) into individual orbitals and places the electron in one of them. It defines the orientation in space of a given orbital of particular energy (n) and shape (I).  Spin quantum number ◦Spin quantum number describes the spin of the electron about it own axis. The values are Examples ◦ Tell how many electrons in a given atom can have the following set of quantum numbers ? 1. n= 4 2. n =4 l= 3 3. N = 1 4. N=6 l =0 Tell which sublevel is described by the given 5. N = 5 l= 3 6. N= 4 l =0 Let us do some exercise ◦ What is the subshell with the quantum number n=4 , l=2 is ______ ◦ What is the subshell with the quantum number n=5 , l=3 is ______ ◦ The magnetic value for a d orbital are ◦ The magnetic value for a f orbital are ◦ The allowed values of l for the shell with n= 2 ◦ The allowed value of l for the shell with n =4 ◦ How many electrons can inhabit all of the n=4 orbitals ◦ How many electrons can inhabit all of the n=2 orbitals Aufbau principle ◦ Aufbau principle, also known as the "building-up" principle, is a fundamental principle in quantum mechanics that governs the electronic structure of atoms. It states that in the ground state of an atom, electrons occupy the lowest-energy orbitals available. Pauli Exclusion Principle ◦The Pauli exclusion principle is a fundamental principle in quantum mechanics that states that no two identical fermions (particles with half-integer spin, such as electrons) can occupy the same quantum state simultaneously. Hund’s rule ◦ if there are multiple orbitals of the same energy level, electrons will first fill each orbital with one electron before pairing up in any orbital. This leads to the maximum possible total spin for the electrons in the atom. RECTANGULAR –ARROW METHOD sublevel Boxes Max Arrows S 1 2 P 3 6 D 5 10 f 7 14 RECTANGULAR –ARROW METHOD Electron configurations 1s 2s 2p Expanded Condensed H 1s1 1s1 He 1s2 1s2 Li 1s22s1 1s22s1 3p Be 1s22s2 1s22s2 3s 2p B 1s 2s 2p 2 2 1 1s 2s 2p 2 2 1 2s Energy C 1s22s22p12p1 1s22s22p2 N 1s22s22p12p12p1 1s22s22p3 O 1s22s22p22p12p1 1s22s22p4 F 1s22s22p22p22p1 1s22s22p5 1s Ne 1s22s22p22p22p2 1s22s22p6 Example problem