DUE DATE: JUNE 25 TH. SUMMER REV: Electron Configurations

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1 NAME: DUE DATE: JUNE 25 TH AP Chemistry SUMMER REV: Electron s Why? The electron structure of an atom is very important. Scientists use the electronic structure of atoms to predict bonding in molecules, the charge(s) an atom might have, and the physical properties of elements. In order for scientists to describe the electron structure in an atom, they give the electrons addresses. Just like your address might include your house number, street, city, and state, an electron s address has multiple parts. In this activity, you will learn how the electrons fill up the available spaces in an atom and how their addresses or configurations are assigned. Success Criteria o Explain the rules for electron placement: aufbau Principle, Pauli Exclusion Principle, and Hund s Rule. o Construct the orbital filling diagrams, electron configurations, and noble gas shortcut configurations for neutral ground-state atoms. o Identify an element from its ground-state orbital filling diagram, electron configuration, or noble gas shortcut configuration. o Identify an element from its excited-state orbital filling diagram, electron configuration, or noble gas shortcut configuration. Vocabulary o Principal Energy Level (n) = fixed energy an electron can have (whole number = 1, 2, 3, 4; written first) o Sublevel = orbitals of the same energy in an energy level (letters = s, p, d, f; written second) o Orbital = region of space where an electron is most likely to be found o Electron Spin = denoted by, show direction of magnetic poles for spinning electrons o Orbital Filling Diagram = electron configuration that uses arrows to depict electrons and demonstrates how each orbital is filled for a sublevel o Electron = arrangement of electrons of an atom in its ground state into the orbitals surrounding the nucleus o Ground State = lowest possible energy of an electron (opposite of Excited State) o Noble Gas Shortcut = using the symbol of a noble gas to represent the stable configuration of electrons instead of writing out a complete electron configuration (ONLY NOBLE GASES!!!) MODEL 1: The Number of Electrons in an Orbital The electron is what is referred to as a spin ½ particle. The electron may be thought of as spinning like a top. If it is spinning with it spin up, it is assigned m s = +½. If it is spinning in the opposite direction, with its spin down, it is assigned m s = -½. The Pauli Exclusion Principle dictates that two electrons within the same orbital must have different values of m s. Two negatives repel, electrons use opposite poles to overcome the repulsion. Since there are only two poles, there can be a maximum of two electrons in an orbital. Key Questions: 1. How many electrons can occupy: a. An s sublevel? b. A p sublevel? c. A d sublevel? d. An f sublevel?

2 S U M M E R R E V : E l e c t r o n C o n f i g u r a t i o n s 2 MODEL 2: Blocks of the Periodic Table Please note that HELIUM has been shifted to Group 2 for the purpose of electron configuration rules. n = 1 n = 2 1s 2s 3s He The square in the upper left (hydrogen) is our starting point, and we proceed from left to right, up to down. The four outlined rectangular regions are referred to as the s block, the p block, the d block, and the f block. Squares within the same period are in the same sublevel if they are in the same block. (In order to determine orbital filling, we must use orbital filling diagrams.) Key Questions: 2. Use your answers to Questions 4 & 5, label the Periodic Table with s block, p block, d block, and f block. 3. Label the n values for each period of the Periodic Table. a. What is the minimum value of n needed to have an s sublevel? Finish labeling the first column of the s block. b. What is the minimum value of n needed to have a p sublevel? Label the first column of the p block in the same manner that the s block was labeled. c. What is the minimum value of n needed to have a d sublevel? Label the first column of the d block, starting with your minimum n value. d. What is the minimum value of n needed to have an f sublevel? Label the first column of the f block, starting with your minimum n value. 4. Theoretically there is a g sublevel for electrons to occupy. Where would elements that fill this sublevel be located? Why?

3 S U M M E R R E V : E l e c t r o n C o n f i g u r a t i o n s 3 MODEL 3: Ground-State Electron s An electron configuration is written to inform the reader in which orbitals the electrons may be found within an atom. The groundstate is the lowest energy state of an atom, where all the electrons reside in their lowest energy positions. For example, hydrogen in the ground-state has a single electron in the 1s orbital. So the ground-state electron configuration of hydrogen is: 1s 1. (The superscript tells the reader how many electrons are in the sublevel.) It is quite easy to write the ground-state configuration of a multi-electron atoms using the blocks of the Periodic Table. Start at Z = 1 (atomic number = 1) and proceed to the atomic number of the element in question, keeping those block designations in mind.

4 S U M M E R R E V : E l e c t r o n C o n f i g u r a t i o n s 4 PRACTICE: 1. Use the periodic table as a guide to write full ground-state electron configurations for: A. Fluorine B. Iron C. Rubidium D. Tin E. Europium 2. For the same elements, write the orbital filling configurations: A. Fluorine B. Iron C. Rubidium D. Tin E. Europium 3. For the same elements, write the noble gas shortcut configurations: A. Fluorine B. Iron C. Rubidium D. Tin E. Europium

5 S U M M E R R E V : E l e c t r o n C o n f i g u r a t i o n s 5 4. Below are three answers generated by students in response to the prompt: Provide an orbital configuration for the groundstate of a nitrogen atom. In each case, indicate whether the answer is right, wrong, and if it is wrong, explain why. EXTENSION QUESTIONS A. Consider the orbital diagram: 1. Identify the element. 2. Is the arrangement of electrons in the orbital diagram higher in total potential energy or lower in total potential energy than the ground state electron configuration? Explain your reasoning. B. Each orbital diagram shown below describes an excited-state of an atom of a different element. Use the diagrams to complete the table. Excited-state Electron Element Identity A B C Ground-state Electron

6 S U M M E R R E V : E l e c t r o n C o n f i g u r a t i o n s 6 C. Complete the table for each of the excited-state electron configurations given. Excited-state Electron Element Name and Symbol Ground-state Electron Orbital Diagram for Ground-state 1s 2 2s 1 2p 2 1s 2 2s 2 2p 2 3s 2 3p 1 D. For each of the following elements, circle the portion of the true electron configuration that differs from the predicted configuration. Give a possible explanation for why the true configurations differ from the predicted configurations. (Be sure to address energy and sublevel stability.)