Warm-up: Identify 3 facts about electrons Where are the electrons? Electrons & Electromagnetic...

• Warm-up: Identify 3 facts about electrons• Where are the electrons?• Electrons & Electromagnetic Radiation

l

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?

Fastest travel to the moon 8 hours, 35 minutesPluto mission fly-by

Distance from Earth to Moon:383,401 km

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

Electrons & Electromagnetic Radiation

• 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

Electromagnetic Radiation

• Form of energy that has a wave-like properties

• Characterized by – Wavelength– Frequency– Energy

Electromagnetic spectrum• See video clips: 1. NASA – saved

– 2. www.teachersdomain.org/resource/phy03.sci.phys.energy.emspectrum/

• Visible light

• Higher energy than visible light

• Lower energy than visible light

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 EducationStarts 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

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– 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

Elements and their electromagnetic radiation

• 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– Write the order of the colors

Hydrogen: Nitrogen:Mercury:Neon:Other:

Emission Line Spectra

Emissions Spectra - Simulation

• http://phet.colorado.edu/en/simulation/discharge-lamps

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 Animationsfor Elements 1-11

• http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-atoms.shtml

• http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-atoms.shtml

Electrons in models of atoms

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.

Exploratory Lab

http://phet.colorado.edu/en/simulation/hydrogen-atom

Quantum Model

• Video – www.teachersdomain.org• http://www.teachersdomain.org/resource/p

hy03.sci.phys.fund.quantum/• (thinking behind current atomic model)• http://www.teachersdomain.org/resource/p

hy03.sci.phys.matter.atoms/• The space in between

Video electron arrangement

• Video – (low volume) • http://ed.ted.com/featured/YlZZblvz

Probable location of the electronThe 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 analogyAspen 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:

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Examples: Sulfur & Iron

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Students:

Phosphorus

Calcium

Krypton

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Incr

easi

ng E

nerg

y

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

1s

1s

1s 2s

1s 2s

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p 3s

Element Atomic # Orbital diagram Electron 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

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!

1s

1s

1s 2s

1s 2s

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p 3s

Element Atomic # Orbital diagram Electron 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– 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

1s² 2s² 2p⁶ 3s² 3p⁴ 1s² 2s² 2p⁶ 3s¹1s² 2s²1s¹

Electron Configuration

Write • Potassium

• Aluminum

• Chlorine

Circle the valence electrons.

Electron Dot Notation

• Represents valence electrons

K Al Cl

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 2p⁶as [Ne]- Use in Na: [Ne] 3s¹

Noble Gas Notation

Element

1s² 2s² 2p⁶ 3s² 3p⁶

1s² 2s² 2p⁶ 3s² 3p⁴ 1s² 2s² 2p⁶ 3s¹

1s² 2s² 2p⁶

Noble Gas Notation

Element1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

3d¹º4p⁶ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁵ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

3d¹º4p⁴ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º

4p¹1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

1s² 2s² 2p⁶ 3s² 3p⁶

Noble Gas Notation

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º 4p⁶ 5s²4d¹⁰ 5p⁵

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶ 5s² 4d¹⁰5p⁴

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶ 5s² 4d¹⁰5p²1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶ 5²1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 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

1 18

2 13 14 15 16 17

3 4 5 6 7 8 9 10 11 12

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 sequenceTi: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d²Energy level sequenceTi: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²