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Nuclear Chemistry
Unit 1-2 Day 8
Half-Life
+
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
+
HOMEWORK CHECK
BLOCK 2 & 4
+
+
+
HOMEWORK CHECK
BLOCK 3
+Half-Life and uses for radiation
Practical uses for nuclear chemistry
+
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
+
+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
+
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?
+
NATURALLY OCCURRING RADIATION HAS ALWAYS BEEN
PRESENT……
+
+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
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