# Warm-up: Identify 3 facts about electrons Where are the electrons?

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Warm-up: Identify 3 facts about electrons Where are the electrons?

Arrangement in the Atom
Electrons Arrangement in the Atom

Where are the electrons?
Electrons are traveling at 6 x 10⁶m/sec around the nucleus Perspective of the speed: How long would it take a space vehicle to travel to the moon at the electron’s speed?

Distance from Earth to Moon: 383,401 km Fastest travel to the moon 8 hours, 35 minutes Pluto mission fly-by

Electrons: Earth to moon distance: 383,401 km Convert to meters
Calculate the time to travel to the moon at the speed of an electron (6 x 10⁶ m/sec): Distance = Time x Speed

By studying the light emitted when heating up a chemical sample, scientists better understood the electron: Its position in the atom; Its energy; & Its role (bonding = forming compounds) Scientists used the electromagnetic radiation to study electrons

Form of energy that has a wave-like properties Characterized by Wavelength Frequency Energy

Electromagnetic spectrum
See video clips: 1. NASA – saved 2. Visible light Higher energy than visible light Lower energy than visible light

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Everyday examples of the Electromagnetic Spectrum

Electrons will give off electromagnetic radiation
When “energized” by heat, electricity, light or chemical reactions. How and why does this happen?

Energy exists in photons
A photon has a specific amount (or packet) of energy Also use the word “quantum of energy” Photons with different energy will have specific wavelengths related to the energy

Bohr’s discovery and model: saved video from Discovery Education Starts with historical perspective

Bohr’s Model of the Atom
Electrons orbit the nucleus at: At the lowest energy level possible Called the ground state Electrons can be excited by: Electricity, light, chemical reactions When excited, an electron will absorb only a certain amount of energy, A “packet” of energy called a photon or quantum

Bohr’s model When excited, the electron
Will jump to a higher energy level Called the excited state The electron does not stay in the excited state but falls back toward the nucleus and releases energy

Bohr’s model

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Bohr provided critical information
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

Emission Spectrum Lab Purpose: To relate the unique emission spectra lines of an element to the energy levels of the atom. Essential Question: What are the emission spectra for specific elements?

This is?

How do neon lights produce the glowing colors?
FACTS: Neon is a colorless, inert (non-reactive, non-flammable) gas Neon lights are tubes filled with neon gas.

Neon atoms Normal conditions Electricity passing through the tube
Electrons are at the ground state No light (energy) is emitted Electricity passing through the tube Atoms absorb energy Electrons become excited and unstable Electrons are pulled back toward the nucleus Electromagnetic radiation is emitted

Emissions spectrum Unique for each element Electrons are excited by electricity When they are pulled back by the ____________, they give off __________

Emission Spectrum White light Hydrogen: Nitrogen: Mercury: Neon:
Write the order of the colors Hydrogen: Nitrogen: Mercury: Neon: Other:

Emission Line Spectra

Emissions Spectra - Simulation
Produce light by bombarding atoms with electrons. See how the characteristic spectra of different elements are produced, and configure your own element's energy states to produce light of different colors.

Emission Spectra Unique for each element
Used to identify elements as part of unknown compounds

Hubble Space Telescope

Bohr Model Animations for Elements 1-11

Electrons in models of atoms
Exploratory Lab How did scientists figure out the structure of atoms without looking at them? Try out different models by shooting light at the atom. Check how the prediction of the model matches the experimental results.

Quantum Model Video – www.teachersdomain.org
(thinking behind current atomic model) The space in between

Video electron arrangement
Video – (low volume)

Probable location of the electron
The electron arrangement represents where an electron can be found 90% of the time.

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?

Where are the electrons?

Electron placement analogy Aspen Hotel

Hotel Analogy – cont

Hotel Analogy – cont

Rules for Electron Arrangement
Aufbau: * Pauli’s exclusion principle: Hund’s rule: * 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:

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

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

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

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

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

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

Electron Configuration
Element Atomic # Orbital diagram Electron Configuration H He Li Be B C N O F Ne Na

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

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

Electron Configuration
Principal energy level + sublevel Use superscripts to show number of electrons in each sublevel 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

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!

Electron Configuration
Element Atomic # Orbital diagram Electron Configuration H He Li Be B C N O F Ne Na

S, P, D, F Blocks Periods 18

Valence Electrons Electrons in the outermost (highest) principal energy level Important Participate in bonds to make compounds 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 1s² 2s² 2p⁶ 3s² 3p⁴ 1s² 2s² 2p⁶ 3s¹ 1s² 2s² 1s¹

Electron Configuration
Write Potassium Aluminum Chlorine Circle the valence electrons.

K Al Cl Electron Dot Notation Represents valence electrons
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] 3s²3p⁵ iron [Ar] 4s²3d⁶ zinc [Ar] 4s²3d¹⁰ barium [Xe] 6s²

Noble Gas Notation Short cut method for electron arrangement
Use the noble gas in the period above the element Example: Na 1s² 2s² 2p⁶ 3s¹ Use Neon Represent neon’s configuration 1s² 2s² 2p⁶ as [Ne] - Use in Na: [Ne] 3s¹

Noble Gas Notation 1s² 2s² 2p⁶ 3s² 3p⁴ Element 1s² 2s² 2p⁶ 3s² 3p⁶

Noble Gas Notation Element 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁵

Noble Gas Notation 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º 4p⁶ 5s²4d¹⁰ 5p⁵

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: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d² Energy level sequence Ti: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²