Electron Arrangement Unit 3

NC Essential Standards Chm Analyze diagrams related to the Bohr model of the hydrogen atom in terms of allowed, discrete energy levels in the emission spectrum. Describe the electron cloud of the atom in terms of a probability model. Relate the electron configurations of atoms to the Bohr and electron cloud models. Chm Understand that energy exists in discrete units called quanta Describe the concept of ground and excited states of electrons in an atom 1. When an electron gains an amount of energy equivalent to the energy difference, it moves from its ground state to a higher energy level. 2. When the electron moves to a lower energy level, it releases an amount of energy equal to the energy difference in these levels as electromagnetic radiation (emissions spectrum). Articulate that this electromagnetic radiation is given off as photons. Understand the inverse relationship between wavelength and frequency, and the direct relationship between energy and frequency. Use the “Bohr Model for Hydrogen Atom” and “Electromagnetic Spectrum” diagrams from the Reference Tables to relate color, frequency, and wavelength of the light emitted to the energy of the photon. Explain that Niels Bohr produced a model of the hydrogen atom based on experimental observations. This model indicated that: 1. an electron circles the nucleus only in fixed energy ranges called orbits; 2. an electron can neither gain or lose energy inside this orbit, but could move up or down to another orbit; 3. that the lowest energy orbit is closest to the nucleus. Describe the wave/particle duality of electrons.

Energy is related to the Electron’s orbits When an atom is: The electron will: –Start at the –Jump to –Number of jumps is related to Key researchers: Bohr, Plank, Einstein Schrodinger Overview

Bohr’s Model of the Atom Electrons orbit the nucleus at: Electrons can be excited by: When excited, an electron will absorb only a certain amount of energy, (

Bohr’s model When excited, the electron –Called the _________ state The electron does not stay in the excited state but falls back toward the nucleus and releases

Bohr’s model

Ground vs. excited state Number of electrons that exist at specific energy levels Bohr’s model works for hydrogen but not for the complex atoms

Development of the Modern Atomic Model Here are several models of the atom as they were developed in history:

Electron Cloud Model Quantum Mechanical Model –Based on determining the probable location of the electron –Within the boundary of the atom, its electrons can be found 90% of the time (based on probability)

Methods for Writing Electron Arrangements Orbital notation Electron configuration Noble gas notation How are you going to remember the names for each method of writing the electron arrangement?

Rules for Electron Arrangement Aufbau: Place the electron at the lowest energy orbital possible. * Pauli’s exclusion principle: Place a maximum of 2 electrons in each orbital. Hund’s rule: Place an electron in each orbital of a sublevel before pairing up. * Check the diagram for the order of increasing energy level

Electron Arrangement Diagram n= principal energy level Sublevels – s, p, d, f Orbitals –Each orbital holds 2 electrons with opposite spins, shown by arrows:

Increasing Energy Nucleus Energy Diagram n = principal energy level Sublevels: Orbitals Electrons & spin

SPUD Farm Memory tool

Principal Energy Level Location of the Valence electrons

Increasing Energy Nucleus Energy Diagram n = principal energy level Sublevels: Orbitals Electrons & spin Examples: Sulfur & Iron

Increasing Energy Nucleus Energy Diagram n = principal energy level Sublevels: Orbitals Electrons & spin Students: Phosphorus Calcium Krypton

Increasing Energy Nucleus Energy Diagram n = principal energy level Sublevels: Orbitals Electrons & spin

Increasing Energy Nucleus Energy Diagram n = principal energy level Sublevels: Orbitals Electrons & spin

Orbital Notation The orbital is indicated by a line____ wioth the name written below. Arrows represent the electrons. Examples Ne: ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ Note: You must write both the lines and the orbital designations under the lines

ElementAtomic #Orbital diagramElectron Configuration H He Li Be B C N O F Ne Na

Practice Element Atomic # (Z) H He Li Be B Orbital Notation ___ 1s ___ 1s ___ 1s 2s ___ 1s 2s ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p

Practice C N O F Ne ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p ___ ___ ___ ___ ___ 1s 2s 2p 2p 2p

Electron Configuration Principal energy level + sublevel Use superscripts to show number of electrons in each sublevel 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ²

Electron Configuration: Sublevel diagram Determining order: Aufbau rules n=1 n=2 n=3 n=4 n=5 see figure 5-19 on p.138 Know how to make this chart!

ElementAtomic #Orbital diagramElectron Configuration H He Li Be B C N O F Ne Na

Check your electron configuration answers using the Periodic Table Periods S, P, D, F Blocks 18

Valence Electrons Electrons in the outermost (highest) principal energy level –Important –Participate in bonds to make compounds –1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 1s ² 2s ² 2p ⁶ 3s ² 3p ⁴ 1s ² 2s ² 2p ⁶ 3s ¹ 1s ² 2s ² 1s¹

Review: Electron Configuration Write Potassium Aluminum Chlorine Circle the valence electrons.

Electron Dot Notation Represents valence electrons KAlCl Maximum number = 8 Octet rule: atoms will lose, gain or share electrons to have 8 valence electrons & become stable

Introducing Noble Gas Notation Analyze the following examples and propose the rules for writing Noble Gas Notation. chlorine [Ne] 3s ² 3p ⁵ iron [Ar] 4s ² 3d ⁶ zinc [Ar] 4s ² 3d ¹⁰ barium [Xe] 6s ²

Noble Gas Notation Short cut method for electron arrangement Use the noble gas in the period above the element Example: Na 1s ² 2s ² 2p ⁶ 3s ¹ -Use Neon -Represent neon’s configuration 1s ² 2s ² 2p ⁶ as [Ne] - Use in Na: [Ne] 3s ¹

Noble Gas Notation Element 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 1s ² 2s ² 2p ⁶ 3s ² 3p ⁴ 1s ² 2s ² 2p ⁶ 3s ¹ 1s ² 2s ² 2p ⁶

Noble Gas Notation Element 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º4p⁶ 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º4p⁵ 1s² 2s² 2p ⁶ 3s² 3p ⁶ 4s ² 3d¹º4p⁴ 1s² 2s² 2p ⁶ 3s² 3p ⁶ 4s ² 3d¹º 4p¹ 1s² 2s² 2p ⁶ 3s² 3p ⁶ 4s¹ 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶

Noble Gas Notation 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º 4p⁶ 5s ²4d¹⁰ 5p⁵ 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º4p⁶ 5s ² 4 d¹⁰ 5p⁴ 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º4p⁶ 5s ² 4 d¹⁰ 5p² 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º4p⁶ 5 ² 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d¹º4p⁶

Periodic Table: Order based on Electron Configuration Identify element –Write atomic number (Z) –Symbol Circle or highlight the valence electrons Write the electron dot notation

Write the Electron Dot in the correct location for the element

Electron Configuration Aufbau is the Rule. Note: However, sometimes the electron configurations are written in energy level sequence rather than Aufbau sequence. This is mostly used for the “d” sublevel. Aufbau sequence Ti:1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d² Energy level sequence Ti: 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 3d ² 4s ²