Chmy 121in 1st Edition Lecture 13Review- Bohr’s model/Theoryo In Bohr’s model, electrons orbit the nucleus like planets around the suno Electrons furthest from the nucleus have the most energy most unstable most likely to react- Orbitalso Electron shells  Shells are assigned principle quantum numbers (n=1,2,3…)  Each shell has a different number of electrons it can hold, equal to 2n2o Electrons generally occupy the lowest shell available AKA ground state- Concept Checko T or F? Orbitals occupy more space as n increases o If n increases and the size increases, how do you expect this to affect the number of electrons a shell can hold?  Each shell can hold 2n2 electronsToday’s Lecture- Energy Shellso • As you move away from the nucleus, the energy differences between levels is less –  Energy level diagrams Shells do not become physically closer- Bohrs Model Predicts Hydrogen Spectrao To determine ground state, put electrons in the lowest energy shells This is the ground state electron configurationo Electron can be excited to higher energy excited stateso Electron can relax to any lower energy shell o Difference between shells determines energy Energy defines color of light- Relaxationo Energy is released during relaxation Either light or heat The amount of energy released determines the wavelength (l) of light and therefore the colorThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Sub shellso • Each shell contains subshellso The number of subshellsdepends on the number ofelectrons in shell –  n = 1 has only s  n = 2 has s and p n = 3 has s, p and d n = 4 has s, p, d, and f- Electron Configurationo We have a short hand notationfor showing how electrons arearranged in an atom. It is calledthe atom’s electronconfigurationo Arsenic Configurationo ---- Hunds Rule- Octet Ruleo Elements react in such way as to place 8 Electrons In their outermost shello Exceptions H, He(2), Be(4),B(6) Some 3rd period elements have more then 8 Group 4 don’t behave Transition metals don’t really follow the rule- Cheat Cheat Electron ConfigurationsLecture - Summary of Groupso IonsAnnouncements- Homework 3 is open and is due Monday Feb. 16 at 11 pm- Exam Scores are posted to D2L- Next Exam March 3Lecture 12- Summary of GroupsGroup Wants to… ChargeIA Lose 1 electron +1IIA Lose 2 electron +2IIIA Lose 3 electron +3VA Gain 1 electron -3VIA Gain 2 electron -2VIIA Gain 3 electron -1- Electron Arrangement affects Ionization Energyo Adding shells means it is a larger atomo Adding proton outweighs adding an electron; which means electrons are held more tightly then protons- Modern Model of an Atomo Initial model of quantized energies was difficult to accept Many scientists were skeptical and predicted strange behaviors- Strange behaviors are now used in technology todayo Heisenberg Uncertainty Principle Cannot know both where an electron is and how fast it is going- Probabilityo The best we can do with electrons is define an area where we might find an electron  Sort of like a fenceo Regions of probability have distinct shapes Orbitals or Subshells- Orbitals increase in size as n increases- Orbitals can overlap in space- Chemical Bondso Holds molecules together Balance between repulsive and attractive forceso Covalent bonds Sharing electorns “Co-“ = sharing “valent”= Valence Electron Only valence electrons take part in covalent bondso Ionic Bonds Covalent look like ionic bonds- Polar Covalent Moleculeso Unequal sharing of electrons results in polar covalent moleculeso Some element have a higher affinity for electrons which means they are held more tightly o Electronegativity Follows a trend similar to ionization energy- Strong Bondso Because electrons are shared between atoms, neither atom wants to leaveo Covalent bonds are very strong and difficult to break Must increase temperature to 3000 degrees Celsius Energy needed is among the highest in Chemistry- Non-Metal bond formationo Hydrogen, Nitrogen, Oxygen, Chloride, Bromine, & Iodine are more stable as two atom molecules(Diatomic molecules)o As the atoms move closer, the attraction of one hydrogens electrons to the other’s neutron increaseso Electrons are shared between atomso Repulsive force between positively charged nuclei prevent further movement - Lewis Dot Structureso Number of valence electrons is determined by the elements locations in the periodic tableo Bond will form with any unpaired electrono Hydrogen has 1 valence electron so when is paired with sulfur that has 6 valence electrons you must put 2 hydrogens to bring it to 8 electrons which is fullAnnouncements- No class Monday but we will stillhave lab and recitations- Unit schedule is posted - Homework 3 is due Monday February 16th by