Introduction to IsotopesNuclear Chemistry, Unit 4

Curricular Map

Nuclear Chemistry

Introduction to Isotopes

Nuclear Fission

Nuclear Fusion

Radioactive Decay

Radioactive Half-Lives

Daily Agenda

1. Radioactive smoke article

2. Review of subatomic particles

3. Definition of an isotope

4. Practice understanding isotopes

5. In-class work/homework

Learning Goals:

By the end of class, you should be able to: Navigate your way around a new way to

represent elements, called Isotope Notation Take information about an isotope and

represent it in Isotope Notation, and vice versa

Great White Sharks

Questions to answer Before Reading

1. What audience was the article intended for?

After Reading 2. What do isotopes have to do with

estimating the age of sharks?

Review : subatomic particles

So…what is an isotope?

Isotopes – atoms of the same element with differing numbers of neutrons

Isotope Analogy: Trucks

1st Isotope of the Ford F-150 : Regular Cab

2nd Isotope of the Ford F-150: Super Cab

3rd Isotope of the Ford F-150: Crew Cab

Isotope Analogy: Trucks

So…what is an isotope?

Isotopes – atoms of the same element with differing number of neutrons

Isotopes of Carbon

Carbon-12 (6 neutrons)

Carbon-13 (7 neutrons)

Carbon-14 (8 Neutrons)

But how do we know exactly how many neutrons an atom has?

• This notation tells you the element and the mass number

• Mass number = sum of protons and neutrons

Isotope Notation

A few examples of isotope notation…

= Carbon-12

= Carbon-13

= Carbon-14

A few examples of isotope notation…

= Carbon-12

= Carbon-13

= Carbon-14

What about the electrons?

If the atomic mass is the sum of the masses of the protons and neutrons, why don’t we count mass of the electrons?

The mass of an electron is about 1/2000th of a proton

If a proton weighs 1, an electron weighs 0.0005, and its mass is negligible

Individual Practice

Write the following isotopes in isotope notation:

Uranium-232

Cadmium-113

Fill in the missing pieces:

Isotope Notation Isotope Name Atomic

NumberMass

NumberNumber of

ProtonsNumber of Neutrons

147 62

Isotope Notation Isotope Name Atomic

NumberMass

NumberNumber of

ProtonsNumber of Neutrons

? Samarium-147 62 147 62 85

Postcard to an absent student

On a half sheet of paper:

Summarize two main ideas from today Give an example of an isotope not used in

my examples

Homework/In-class work

Isotope Notation worksheet

Curricular Map

Nuclear Chemistry

Introduction to Isotopes

Nuclear Fission

Nuclear Fusion

Radioactive Decay

Radioactive Half-Lives

Daily Agenda

1. Entrance card: Isotopes

2. Warmup: Averages

4. Group work: Weighted averages

5. Closing: Postcard to an absent peer

Essential Questions

What is a weighted average?

Why is the mass of a single isotope of an element different than the mass on the periodic table?

How can the concept of weighted averages be applied to isotopes?

Learning Goals:

By the end of class, you should be able to:

Explain what a weighted average is, compared to an unweighted average

Calculate a weighted average Apply the idea of a weighted average to

isotopes

Essential question: How can the concept of weighted averages be applied to isotopes?

Atomic Mass

The mass on the periodic table is a weighted average of all of the isotopes of that element.

Essential question: What is a weighted average?

Investigation

Section A of chemistry has 20 students in it, and section B of chemistry has 30 students in it. The average grade in section A was 80%, and the average grade in section B was 90%. What is the:

A.) Unweighted average of all chemistry students? 85%

B.) Weighted average of all chemistry students? 86%

Formula for calculating the unweighted average:

Formula for calculating the weighted average:

What’s different?

= 86

= 85

Group work: Weighted and unweighted averages

In groups of 2-4, work on the “Concept Work: Weighted Averages” worksheet, through section B

Postcard to an absent peer

On a half-sheet of paper, describe: A major idea from today that you

understand well An idea that you want to work more

with

Notes From Exit/Entrance Cards

No memorizing formulas!

Differentiating weighted/unweighted averages Our work with weighted/unweighted

averages was mostly to highlight what a weighted average is

Check emails for entrance card notes

Curricular Map

Nuclear Chemistry

Introduction to Isotopes

Nuclear Fission

Nuclear Fusion

Radioactive Decay

Radioactive Half-Lives

Daily Agenda

Notes from entrance cards

Mini-lesson: Average atomic mass

Concept mapping

Pseudo-exit cards: Concept mapping

In-class work/homework: Average atomic mass

Essential Questions

What does the mass on the periodic table represent?

How is each isotope accounted for in the average atomic mass of an element?

How can we connect the ideas we’ve covered so far?

Learning Goals:

By the end of class, you should be able to:

Calculate the average atomic mass of an element, given the masses of the isotopes of that element

Map and describe the ideas we’ve covered so far in this unit with a 70% comfort level

Atomic Mass

The mass on the periodic table is a weighted average of all of the isotopes of that element.

Practice: Average atomic weight

A sample of Dubnium contains two different isotopes. The first isotope, Dubnium-265, has an abundance of 40%. The second isotope, Dubnium-260, has an abundance of 60%. What is the average atomic weight of Dubnium?

Does is match the mass of Dubnium found on the periodic table?

Practice: Average atomic weight

A sample of Cerium contains two different isotopes. The first isotope, Cerium-122, has an abundance of 4.65%. The second isotope, Cerium-141, has an abundance of 95.35%. What is the average atomic weight of Cerium?

Does it match the mass found of Cerium found on the periodic table?

Concept Mapping

To connect what we’ve covered in this unit so far, describe each component of the concept `map and how it is related to what it is connected to.

While you’re working, if you come upon a component of the concept map you’re not 70% comfortable with, write it on a half-sheet of paper (exit card) and turn it in!

Work in pairs, please!

In-class work/homework

“Average Atomic Mass” worksheet

Due Friday, January 31st at the beginning of class

QUIZ MONDAY (OPEN NOTES)!

General Announcements

If you are absent, you are responsible for doing the make-up work outside of class time. Send me an email, and we can arrange a time to meet to go over the missing material. www.mauhschemistry.wikispaces.com

Notes From the Quiz

If I wrote “see key”, I’m not posting it to the WikiSpace because there are still people that haven’t taken the quiz. See me for it.

Curricular Map

Nuclear Chemistry

Introduction to Isotopes

Nuclear Fission

Nuclear Fusion

Radioactive Decay

Radioactive Half-Lives

Daily Agenda

Video: Bernie!

Mini-lesson: Nuclear fission and fusion

In-class work/homework

Essential Questions

How is a nuclear reaction different than a chemical reaction?

What is nuclear fission? Fusion?

How does the mass of a nucleus predict the probability of either nuclear fission or fusion reactions?

Learning Goals:

By the end of class, you should be able to: Describe how a nuclear reaction is different

than a chemical reaction Differentiate nuclear fission and nuclear

fusion Balance a nuclear reaction and identify it as

either a fission or fusion reaction Predict whether an element is more likely to

undergo fission or fusion, based on its mass

Chemical Reactions

2Fe + 3H2SO4 Fe2(SO4)3 + 3H2

Count the atoms of each element on the left.

Do the same for the right.

Do they match?

Nuclear Reactions (fission, specifically)

• Count the atoms of each element on the left (not the middle).

• Count the atoms of each element on the right (not the middle).

• Do they match?

One Missing Component of Fission Reactions

Energy!

+ Lots and Lots of Energy

Comparing Fission & Fusion

So…

Energy is released by splitting very large nuclei or by combining two small nuclei Iron is the “middle” atomic weight Atoms larger than iron are more likely to undergo

fission Atoms smaller than iron are more likely to undergo

fusion

Comparing Fission & Fusion

Fission or Fusion?

Daily Agenda

Warm-up: Chemistry lab write-up rubric

Example: Determining purpose using an abstract

Individual/small group work: Upacking peer-reviwed literature

Essential Questions

How is a peer-reviewed journal article organized in terms of breadth and specificity?

What goes into a research project?

Learning Goals

By the end of class, you should be able to:

Analyze a graph’s data in terms of the variables used on the axes

Summarize the purpose, methods, and implications of a research paper

Identify the methods and instrumentation used to gain data in a study

Example: Abstract

The nuclear accident of Fukushima Dai-ichi (Japan) which occurred after the tsunami that impacted the northeast coasts of Japan on March 11th, 2011 led to significant releases of radionuclides into the atmosphere and resulted in the detection of those radionuclides at a global scale. In order to track airborne radionuclides from the damaged reactors and to survey their potential impact on the French territory, the French Institute of Radiation Protection and Nuclear Safety (Institut de Radioprotection et de Sureté Nucléaire IRSN) set up an enhanced surveillance system to give quick results as needed and later give quality trace level measurements. Radionuclides usually measured at trace levels such as 137Cs and in a very sporadic way 131I were reported.

Curricular Map

Nuclear Chemistry

Introduction to Isotopes

Nuclear Fission

Nuclear Fusion

Radioactive Decay

Radioactive Half-Lives

Daily Agenda

Warmup: Chernobyl

Mini-lesson: Radioactive decay

Individual/small group work: Predicting decay products

Homework: Balancing radioactive decay reactions

Essential Questions

What is spontaneous decay?

Why does an atom spontaneously decay?

How can we predict spontaneous decay products?

Learning Goals:

By the beginning of next class, you should be able to: Define spontaneous decay Explain why spontaneous decay happens Analyze the “belt of stability” Predict decay products and balance a

nuclear reaction

Spontaneous Decay

Definition: the process by which an unstable atom emits particles from its nucleus with the intent of becoming more stable

What is this “stability” concept you speak of?

Example

Two isotopes: Silicon-30 Silicon-28 What are their proton:neutron ratios? Which isotope is more stable? Which isotope is more likely to emit a

particle?

What particles are emitted?

Can we predict decay products?

Example

Predict the decay products (and write the reaction): Phosphorus-33

Lawrencium-260

Upcoming Class Meetings

Friday (2/14) – Quiz Review

Tuesday (2/25) – Quiz

Post-Quiz Homework

Read section C.1 , starting on page 521.

Answer the following questions, on pages 538 and 539: 1,2,3,4,20,21,24

Curricular Map

Nuclear Chemistry

Introduction to Isotopes

Nuclear Fission

Nuclear Fusion

Radioactive Decay

Radioactive Half-Lives

Daily Agenda

Pennies!

Mini-lesson: Modeling half-lives

Individual/small group work: Half-life equations and tables

Homework: Half-lives…and more!

Essential Questions

How can radioactive decay be modeled?

How can we describe radioactive decay?

Learning Goals:

By the beginning of next class, you should be able to: Define half-life Describe the exponential decay function in terms

of half-lives and amount of starting material Determine half-life for an element, given a rate

of decay (or vice versa) Use an equation to determine number of half

lives passed, amount of starting material, and amount of starting material present after a given number of half-lives