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Nuclear Chemistry

Unit 1-2 Day 8

Half-Life

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WARM-UP

Complete the warm-up in your notebook today !

+Today’s Objectives

■ Identify the practical uses of nuclear chemistry

■Define half life.

■Calculate the mass of remaining radioactive element given the half life.

+Warm-Up - Complete In Your NotebookNext slide also for #4

(1) Write the alpha decay reaction for the following:

_______ + __________

(2) Write the beta decay reaction for the following:

________ + __________

(3) Copy and complete the following chart:

Atomic

Symbol

Notation

Atomic # # Neutrons # Protons # Electrons Charge Atomic

Mass

82 +4 208

Ti 25 46

+Warm-Up - Complete In Your Notebook (pg 2)

(4) Calculate the average atomic mass of the following isotopes:

+Element / Symbol Practice

After you complete the warm-up...practice matching elements/symbols

Set 1: Click Here for Set #1

Set 2: Click Here for Set #2

+Warm-Up■ (1) Write the alpha decay reaction for the following:

■ (2) Write the beta decay reaction for the following:

3)

(4) 0.5186 * 106.90509= 55.44 amu

0.4814 * 108.90470= 52.43 amu

107.9 amu

Atomic

Symbol

Notation

Atomic # # Neutrons # Protons # Electrons Charge Atomic

Mass

82208Pb +4 82 126 82 78 +4 208

2246Ti -3 22 24 22 25 -3 46

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HOMEWORK CHECK

BLOCK 2 & 4

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HOMEWORK CHECK

BLOCK 3

+Half-Life and uses for radiation

Practical uses for nuclear chemistry

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Click to Watch Video

■ Copy the following question in your notebook and answer while watching a short video on nuclear radiation, answer the following questions....

(1) What are some practical uses of radiation today?

DO THIS SLIDE AT HOME

+

Half-Life Problem Solving

+ Half-Life■ Measurement “unit” for radioactive decay.

■ Time for half of the original sample to decay

■ Different half-life for each radioactive isotope.

+Example

■How much of a 100 g sample of iodine-131 will be left after 36 hours if the half life is 12 hours?

# Half Lives Elapsed Time Amount

+Example■One product of a nuclear reactor (waste) is the

isotope cesium-137. It has a half-life of 30 years. If 10.0 g of cesium-137 is produced in a nuclear power plant, how much of it would remain after 90 years?

# Half Lives Elapsed Time Amount

+Example ■ In 5.49 seconds, 1.20 g of argon-35 decay to

leave only 0.15 g. What is the half-life of argon-35?

Half –Life Count Elapsed Time Mass

+Video Lesson: Half-Life Problem Solving

Watch the following video on solving problems involving half-life. Be sure to take notes.

VIDEO LESSON: HALF-LIFE

PROBLEM SOLVING

+Half Life StepsDetermine what the problem is looking for.

■ IF the problem is looking for total time past, THEN multiply the number of half lives by the length of one half life.

■ IF the problem is looking for the length of one half life, THEN divide the total amount of time by the number of half lives.

■ IF the problem is looking for the mass left after a period of time, THEN determine the number of half lives and divide the original amount by two that many times.

+

Half-Life Practice Problems

-- Read the problem, highlight the key parts-- Set up chart to solve problems -- Don’t forget the two “0”s in the first row of the chart

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+You Try -- Solve these in your notebook

1)Sodium-24 has a half-life of 15 hours. How much

sodium-24 will remain in an 18.0 g sample after 60

hours?

2)After 42 days a 2.0 g sample of phosphorus-32

contains only 0.25 g of the isotope. What is the

half-life of phosphorus-32?

3) Polonium-214 has a relatively short half-life of

164 seconds. How many seconds would it take

for 8.0 g of this isotope to decay to 0.25 g?

4) What’s the half-life of

the substance in the graph?

+Answers to “YOU TRY” Problems

+(1) Sodium-24

Elapsed Time Quantity

0 18.0 g

15 hrs 9.00 g

30 hrs 4.50 g

45 hrs 2.25g

60 hrs 1.125g remains

+Phosphorous-32

Half – Life Count Amount Elapsed Time

0 0.25 0

1 0.50 14

2 1.00 28

3 2.00 42

42 days / 3 half-life cycles= 14 days is the Half-Life

+Polonium-214

Half-Life Count Amount of Sample Elapsed Time

0 8.0 0 sec

1 4.0 164 sec

2 2.0 328

3 1.0 492

4 0.50 656

5 0.25 820 sec

# half-lives X time for 1 half-life=

5 X 164 = 820 secs

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The original sample is 80 g at 0 days. ½ of 80 grams = 40 grams…. draw line across from 40 until it touches the line on the graph. Connect that point down to the time (days).

It takes 6 days for the original 80 grams to decay to 40 grams. Thus… the half-life is 6 days

+Objectives

■ Identify the practical uses of nuclear chemistry

■Define half life.

■Calculate the mass of remaining radioactive element given the half life.

+CLASSWORK / HOMEWORK

■Exit Ticket■ HALF-LIFE WORKSHEET (1-7)

■ BRING SKITTLES TOMORROW for Lab

■ TEST !!! 2.9.18 - UNIT 2■Element/Symbol Set #2: Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Bromine, Krypton, Rubidium, Strontium, Silver, Cadmium, Tin, Iodine, Xenon, Barium, Gold, Mercury, Lead, Radon

■Quizlet: Element Names & Symbols - Set 2

+Exit Ticket

1. How many days does it take for 16 g of palladium-103 to decay to 1.0 g if the half-life of palladium-103 is 17 days? Round your answer to the nearest two decimal places.

2. All isotopes of technetium are radioactive, but they have widely varying half-lives. If an 800.0 g sample of technetium-99 decays to 100.0 g of technetium-99 in 639,000 yr, what is its half-life? Round your answer to the nearest two decimal places.

+HOMEWORK

■ HALF-LIFE WORKSHEET (1-7)

■ BRING SKITTLE ON WEDNESDAY for Lab

■ TEST Friday 2.9.18!!! - UNIT 2

+Exit Ticket

■How many days does it take for 16 g of palladium-103 to decay to 1.0 g? The half-life of palladium-103 is 17 days.

■All isotopes of technetium are radioactive, but they have widely varying half-lives. If an 800.0 g sample of technetium-99 decays to 100.0 g of technetium-99 in 639 000 y,what is its half-life?

+

Activity

Personal Exposure To Radiation

+Objectives

■ Differentiate between naturally occurring and manmade radiation

■ Identify different sources of radiation

■ Compare amounts of radiation exposure from a variety of common sources

+What are sources of radiation that you feel have the most potential danger?

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NATURALLY OCCURRING RADIATION HAS ALWAYS BEEN

PRESENT……

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+Unit of radiation exposure

■Base = rem

■Typically expressed as milli-rem

■How many millirem are in 1 rem?

+How Radioactive Are You????Type of Radiation (AMOUNT OF mrem PER YEAR EXPOSURE) Amount

(mrem)

FROM SPACE ( 26 mrem at sea level)

add 1 rem for Charlotte @ 850 ft above sea level

FROM THE GROUND (16 mrem – Atlantic States)

FROM FOOD, WATER, AND AIR (24 mrem)

FROM BUILDING MATERIALS

if you live in a wood structure (5 mrem)

if you live in a brick structure (7 mrem)

FROM JET PLANE TRAVEL

for each 2500 miles (1 mrem)

FROM NUCLEAR POWER PLANTS (O.1 if live near a plant)

RADIOACTIVE WASTE DISPOSAL (avg USA dose is 1.0 mrem)

FROM CIGARETTE SMOKE

if exposed to cigarette smoke on a regular basis per ½ hr each day = 50 mrem

If you smoke ½ pack cigarettes per day (750 mrem)

1 pack per day (1500 mrem)

+How Radioactive Are You????

Type of Radiation Amount

(mrem)

FROM MEDICAL DIAGNOSIS (X-RAYS)

CHEST (6 mrem)

PELVIS AND HIPS (65 mrem)

ARMS, HANDS, LEGS, FEET (1 mrem)

SKULL, HEAD, NECK (20 mrem)

MAMMOGRAM (400 mrem)

YOUR TOTAL:

HUMAN LINE PLOT OF RESULTS

+SUPPLIES NEEDED FORIN-CLASS ATOM PROJECT TUESDAY, SEPTEMBER 17, 2013■ ½ SHEET OF POSTER PAPER

■ 3-4 SHEETS OF TYPING PAPER

■ 4 PHOTOS RELATED TO SELECTED ELEMENT ■ No larger than ¼ sheet of paper

■ Color

■ Cut prior to coming to school

■ 1 is for the chemical symbol / 2 illustrate the uses of element / 1 – your choice

■ Glue Stick

■ Marker(s)

■ Colored pencils/Crayons