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Isotope Formulae, Quantum Numbers & Electron Configurations …pretty lofty stuff Isotope Formulae • Provide element’s symbol • Mass number – mass# = #p+ + #n – written as a superscript to the left • Atomic number – atomic# = #p+ or #e- – written as a subscript to the left Isotope Formulae Mass# Atomic# X Carbon has two naturally occurring isotopes: carbon-12 and carbon-13 12 13 6 C 6 C Isotope Formulae Give the isotope formula for each of the following: 3 1. Hydrogen with 2 neutrons 1 H 18 2. Fluorine with 9 neutrons 9 F 235 3. Uranium with 143 neutrons 92 U Valence Electron(s) • The electron(s) farthest from the nucleus or in the outermost energy level. Aufbau Principle • Comes from German word meaning “to build” • Electrons will occupy lower energy orbitals first Pauli Exclusion Principle • An atomic orbital can hold at most two electrons. • If an atomic orbital holds two electrons, they must have opposite spins. Hund’s Rule • When filling atomic orbitals of equal energy, place electrons with parallel spins in the orbitals first. Then, place the oppositely spinning electrons in to the orbitals. Quantum Numbers • Similar to your address • Describe where electrons live within an atom • Four quantum numbers for every electron of every atom Quantum Numbers • Principal (n) – Describes the energy level in which the electron lives – May be any positive integer – Thus, 1, 2, 3, etc. Quantum Numbers • Azimuthal or angular mometum (l ) – Azimuth means course or bearing – Describes the shape of the pathway that the electron takes or the shape of the atomic orbital – May be any integer from zero to (n- 1)…it’s dependent on “n” – Thus, when n=1, l can only be 0 Quantum Numbers • Magnetic (ml ) – Describes the orientation of the atomic orbital in 3-D space – May range from -l to +l …it’s dependent on “l” which is dependent on “n” – Thus, when n=1, l can only be 0, and ml can only be 0 – When n=2, l can be 0 or 1, and when l is 1, ml can be –1, 0, or +1…or three places in space Quantum Numbers • Spin (ms ) – Describes the spin of the electron – May be either –½or +½, it’s dependent upon none of the other quantum numbers – Thus, when n=1, l can only be 0, and ml can only be 0, but ms can be either –½or +½ The Quantum Numbers name symbol values Principal Quantum any positive integer n Number from 1 to infinity Azimuthal Quantum l any integer from 0 to n- Number 1 Magnetic Quantum ml any integer from -l to +l Number Spin Quantum ms - ½ or + ½ Number Quantum Numbers • What are the four quantum numbers of hydrogen’s electron? n=1 l=0 ml = 0 ms = –½ Quantum Numbers • What are the four quantum numbers of all of boron’s five electrons? n=1 n=1 n=2 n=2 n=2 l=0 l=0 l=0 l=0 l=1 ml = 0 ml = 0 ml = 0 ml = 0 ml = -1 ms = –½ ms = +½ ms = -½ ms = +½ ms = -½ Quantum Numbers • What are the four quantum numbers of sodium’s valence electron? n=3 l=0 ml = 0 ms = –½ Electron Configurations • Also describe where electrons live within an atom • It’s like a translation of quantum numbers. • They give the energy level, atomic orbital, and number of electrons residing in the orbital and energy level. Electron Configurations • Energy level – May be any positive integer – Just like the principal quantum number Electron Configurations • Atomic Orbital or Sublevel – Represented by letters: s, p, d, f – Translates azimuthal number and magnetic number – s is the same as l = 0 – p is the same as l = 1 – d is the same as l = 2 – f is the same as l = 3 Electron Configurations • Number of Electrons – in either an atomic orbital or a sublevel – max of 2 in the s sublevel – max of 6 in the p sublevel – max of 10 in the d sublevel – max of 14 in the f sublevel Electron Configurations • Use the periodic table to guide you in writing electron configurations. • Find the link between 2,6,10, and 14 and the periodic table. Electron Configurations • What are the four quantum numbers of hydrogen’s electron? What is the electron configuration of hydrogen? # of n=1 energy 1s 1 electrons level l=0 ml = 0 sublevel/ orbital ms = –½ Electron Configurations • Write the e- configurations of the next 9 elements (through Ne). He…1s2 Li… 1s22s1 Look at the sum of the superscripts… Be… 1s22s2 B… 1s22s22p1 Electron Configurations C… 1s22s22p2 N… 1s22s22p3 O… 1s22s22p4 F… 1s22s22p5 Ne…1s22s22p6 Electron Configurations • Shorthand configurations are written by assuming that you can let the symbol of the noble gas preceding the valence electrons represent the e- configuration to that point. Electron Configurations …shorthand He…1s2 Li… [He]2s1 Be… [He]2s2 B… [He]2s 22p1 C… [He]2s 22p2 Electron Configurations …shorthand N… [He]2s22p3 O… [He] 2s22p4 F… [He] 2s22p5 Ne…[He] 2s22p6 Electron Configurations …shorthand Na… [Ne]3s1 Si… [Ne] 3s23p2 Cl… [Ne] 3s23p5 Ar… [Ne] 3s23p6 Electron Configurations …shorthand Ca…[Ar]4s2 Sc… [Ar] 4s23d1 Mn…[Ar] 4s 23d5 Se… [Ar] 4s23d104p4 Electron Configurations …shorthand I… [Kr] 5s24d105p5 La… [Xe] 6s25d1 Ce…[Xe] 6s 25d14f1 Hg…[Xe] 6s24f145d10 Exceptional Electron Configurations…shorthand Cr… [Ar] 4s23d4 [Ar] 4s13d5 Cu…[Ar] 4s23d9 [Ar] 4s13d10 Mo…[Kr] 5s 24d4 [Kr] 5s14d5 Ag…[Kr] 5s24d9 [Kr] 5s14d10 Orbital Diagrams • Show the electron configuration while illustrating the Aufbau Principle, Pauli Exclusion Principle, and Hund’s Rule • Place energy on the y-axis • Use lines to represent orbitals • Use up and down arrows to indicate spin Orbital Diagrams (template) 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Orbital Diagram for H 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Orbital Diagram for He 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Orbital Diagram for Be 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Orbital Diagram for C 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Orbital Diagram for O 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Orbital Diagram for P 3px 3py 3pz 3s E 2px 2py 2pz 2s 1s Wrap-Up • Write the 4 quantum numbers for each of nitrogen’s 7 electrons. • Write the electron configuration for nitrogen. • Write the orbital diagram for nitrogen.

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posted: | 3/23/2012 |

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