Download Isotopes - Ms. Bergman`s Classes at DCIS Montbello

Isotopes
2-7
October 23 – 24, 2014
Goals
 Students know
 Definition of isotope
 Difference between atomic mass and mass
number
 Students can
 Calculate average atomic mass
 The number of protons, neutrons, and mass
number when given 2 of the variables
Do Now
 Describe 2 differences between
ionic and covalent bonds
 What is the chemical formula of
diphosphorous pentaoxide?
 What is the chemical formula of
magnesium oxide?
Do Now
 Describe 2 differences between ionic and covalent
bonds
 Ionic bonds – metal + nonmetal; valence
electrons are taken/given
 Covalent bonds – nonmetal + nonmetal;
valence electrons are shared
 What is the chemical formula of diphosphorous
pentaoxide?
 P2O5
 What is the chemical formula of magnesium oxide?
 MgO
Objective
 I can calculate the average
atomic mass of the isotope
candium (Cm) using the
Candium Lab analysis.
Agenda
1. Do Now, Objective (7 min)
2. Ionic & Covalent Compounds Quiz (10 min)
3. Introduction to Isotopes (15 min)
4. Isotope Whiteboard Problems (10 min)
5. Calculating Average Atomic Mass (10 min)
6. Candium Lab (30 min)
7. Independent Practice Time (10 min)
Introduction to isotopes
 http://www.brainpop.com/science
/matterandchemistry/isotopes/
 Questions to Consider
• What is an isotope?
• What isn’t atomic mass an even
number?
Think pair share: isotopes
• How do neutrons keep the
protons in a nucleus together?
• The neutrons hold the positive
protons together like glue in
the nucleus
Think pair share: isotopes
• What does an element’s mass number tell
you?
Mass number = # of protons + # of neutrons
isotope
 Atoms of the same element with different
numbers of neutrons.
Example: Two Isotopes of
Sodium
How are isotopes
represented?
A: Mass Number:
#protons + # neutrons
in the nucleus
Always larger than Z
Z: Atomic number:
#protons
X: element symbol
Isotopes of Sodium
23
11
Na
24
11
Na
2 Ways to write
Isotope Symbol
Mass Number
23
element symbol
11
Na
Atomic number
Mass Number
Or Sodium-23
# of Neutrons = Mass Number – Atomic Number
Class problem
 Write the isotope symbol for the
chemical element that has 6
protons and 8 neutrons (write the
symbol both ways)
Class Problem
 Write the isotope symbol for the
chemical element that has 6
protons and 8 neutrons (write the
symbol both ways)
14
C
6
Carbon-14
Work it Out!
 Take out Whiteboards and
Markers
 Talk over answer with partner
 Raise board when directed
#1
 Write the isotope symbol for
the chemical element that
has 17 protons and 16
neutrons
33
17
Cl
17p + 16n = 33 mass number
or
Chlorine-33
#2
How many protons are in the
isotope 54Cr? (Chromium-54)
24 (like every atom of
Chromium)
#3
How many neutrons are in the
isotope 42Ca?
Mass Number 42 = 20p + ?
22 neutrons
#4
How many electrons are in the
isotope 23Na?
Na has 11 protons, so if its neutral it has 11 electrons
11 electrons
Average Atomic Mass
 the weighted average of the atomic
masses of all naturally occurring
isotopes of an element.
Where do we find the
average atomic mass?
ON THE PERIODIC
TABLE!
Average Atomic
Mass
What is the difference??
 The A or ‘Mass
Number’ is the mass
of that specific
isotope
 The number on the
periodic table is the
average of all the
existing isotopes
Isotopes have occur at
different rates…
Isotope
Copper-63
Copper-65
Mass
Number
63
65
Percentage
Natural
Abundance
69.17%
30.83%
ABUNDANCE IS HOW OFTEN THAT
ISOTOPE OCCURS IN NATURE
Steps to finding Average
Atomic Mass
1. Convert Percent Natural Abundance to
Decimal form (divide by 100)
2. Multiply decimal by Mass Number (for
each isotope)
3. Add the product for each isotope
together
Calculating the average atomic mass
Isotope
Copper-63
Copper-65
Mass
Number
63
65
Percentage
Natural
Abundance
69.17%
30.83%
Step 1: Change the percent abundance to decimals.
69.17%/ 100 = .6917
30.83%/ 100 = .3083
Step 2: multiply the mass number by decimal for each isotope
63 x 0.6917 = 43.577
65 x 0.3083 = 20.040
Step 3: add the product of each isotope together
43.577 + 20.040 = 63.61 amu
Quick Write
Isotope
Rubidium-85
Rubidium-87
Mass
Number
85
87
Percentage
Natural
Abundance
72.2%
27.8%
Will the average atomic mass be closer to
85 or 87? Explain your reasoning in a
complete sentence.
You Try!
Isotope
Rubidium-85
Rubidium-87
Mass
Number
85
87
Percentage
Natural
Abundance
72.2%
27.8%
Step 1: Change the percent abundance to decimals.
72.2%/ 100 = 0.722
27.8%/ 100 = 0.278
Step 2: multiply the mass number by decimal for each isotope
85 x 0.722 = 61.37
87 x 0.278 = 24.286
Step 3: add the product of each isotope together
61.37 + 24.286 = 85.56 amu
Candium!
Take 2 mins to SILENTLY read the objective and
introduction.
On your desk Electronic balance
 A candy Cup – do not eat any now you will have a
chance later
 You will be writing down observations on a
separate piece of paper and attaching it to
your lab worksheet
 You will be following the procedure and filling
out the data tables on your lab.
Candium Procedures
1. Put a piece of paper on your balance and zero it (press
‘tare’)
2. Put all of the candium on the balance and find its total
mass (row A, under ‘total’)
3. Count the total number of particles (row B, under total)
4. Put all the plain candium on the balance (row A, 1st
isotope)
5. Count the particles of plain candium (row B, 1st isotope)
6. Repeat steps 4-5 with peanut candium (2nd isotope) and
peanut butter candium (3rd isotope)
7. Show Ms. Bergman your work to move on to the data
analysis section of your lab.
Tonight!
 Complete your isotope
homework!
Isotopes & Average
Atomic Mass
Day 2
Do Now
Answer all 3 – proficient; 2 – partially proficient; 1 – not proficient
 Write both isotope symbol for an atom
with 5 protons and 7 neutrons - easy
 How can you find the number of
neutrons an atom has using the
isotope symbol? - easy
 Define ‘isotope’ - easy
Do Now

Write both isotope symbol for an atom with 5 protons and 7 neutrons easy

Boron (B) has 5 protons

Mass number = 5 + 7 = 12
12 B
5


How can you find the number of neutrons an atom has using the
isotope symbol? – easy

Mass number – atomic number

Boron-12  12 – 5 = 7; 7 neutrons
Define ‘isotope’ – easy

Atoms of the same element with different numbers of neutrons; for
example, Boron-12 and Boron-11
Objectives
 I can calculate the average atomic
mass of the isotope candium (Cm) using
the Candium Lab analysis.
 I can use my understanding of Unit 2-
Atomic Structure to complete the Unit 2
Test Review Guide
Agenda
1. Do Now, Objective (10 min)
2. Candium Lab Analysis (20 min)
3. Average Atomic Mass Whiteboard Problems (10 minutes)
4. Unit 2 Self-Assessment (5 min)
5. Unit 2 Review Guide Independent Work Time (55 min)
Candium Lab Analysis
 All groups should have completed Data
Table 1
 Did you label which isotope is which candy?
Candium Lab Analysis –
Data Table 2

Fill in Data Table 2 using the math in steps 1-5 from your analysis directions.

You MUST show all calculations on a separate sheet of paper

All calculations must be properly labeled.


Example: average mass of candy for the ‘total’ is calculated in step 1, so label it 1a
Ms. B’s class calculators may be used – NO PHONES
Candium Lab Analysis
Questions
 Questions 6 & 7 should be answered on
data table 2 (where labeled 6 and 7
 Questions 7 through 10 should be answered
on a separate sheet of paper and be
properly labeled
 Use complete sentences
 Check your lab against the grading rubric to
make sure you have everything needed
Calculating Average Atomic Mass
Whiteboard Problems
 You need:
 1 calculator per table
 1 whiteboard per table
 1 marker per table
 Notes
Steps to finding Average
Atomic Mass
1. Convert Percent Natural Abundance to
Decimal form (divide by 100)
2. Multiply decimal by Mass Number (for
each isotope)
3. Add the product for each isotope
together
Whiteboard Problem 1 - easy
Isotope
Titanium-46
Titanium-47
Titanium-48
Titanium-49
Titanium-50
Mass Number
46
47
48
49
50
Percent Natural
Abundance
8.0%
7.8%
73.4%
5.5%
5.3%
Calculate the average
atomic mass of Titanium
Whiteboard Problem 1 - easy
Isotope
Mass Number
Percent Natural
Abundance
Titanium-46
46
8.0%
Titanium-47
47
7.8%
Titanium-48
48
73.4%
Titanium-49
49
5.5%
Titanium-50
50
5.3%
Calculate the average atomic mass of Titanium
1.
Convert % natural abundance to decimal form (divide by 100)
46  8.0/100 = 0.08; 47  7.8/100 = 0.078; 48  73.4/100 = 0.734; 49  5.5/100 = 0.055; 50  5.3/100 = 0.053
2.
Multiply mass number by decimal for each isotope
46*0.08 = 3.68; 47*0.078 = 3.666; 48*0.734 = 35.232; 49*.055 = 2.695; 50*.053 = 2.65
3. Add products for each isotope together
3.68 + 3.666 + 35.232 + 2.695 + 2.65 = 47.923
Whiteboard Problem 1 - medium
Uranium is used in nuclear reactors and is a rare
element on earth. Uranium has three common
isotopes. If the abundance of Uranium-234 is
0.01%, the abundance of Uranium-235 is 0.71%,
and the abundance of Uranium-238 is 99.28%,
what is the average atomic mass of uranium?
Whiteboard Problem 1 - medium
Uranium is used in nuclear reactors and is a rare
element on earth. Uranium has three common
isotopes. If the abundance of Uranium-234 is
0.01%, the abundance of Uranium-235 is 0.71%,
and the abundance of Uranium-238 is 99.28%,
what is the average atomic mass of uranium?
Whiteboard Problem 3 - advanced
Complete the table below
Whiteboard Problem 3 - advanced
Complete the table below
Unit 2 Self-Assessment
Rate yourself on each of the big concepts
from Unit 2. Mark this rating on your Unit 2
Review Guide.
A = advanced; P = proficient; PP = partially proficient; U = unsatisfactory
1.
Subatomic Particles & Atomic Structure
2.
Periodic Table Trends
3.
Historic Models of the Atom
4.
Electron Configuration
5.
Valence Electrons
6.
Ionic Bonds
7.
Covalent Bonds
8.
Isotopes & Average Atomic Mass
Unit 2 Review Guide
 Work independently on completing your
Unit 2 Review Guide
 Work with a friend
 Start with the hard stuff first
 Use your notes
 Ask Ms. B for help
 Come to the test review sessions

Monday/Tuesday/Thursday – lunch

Thursday – after school

Thursday – before school (7 AM)
Unit 2 Review Day – 45
Minutes
 Goals
 Check students’ self-assessment scores
 Students complete key assignments/work
that will help them move towards
proficient/advance on different individual
measures from Unit 2
Do Now
 Write down 3 things that you WILL
DO to prepare for
Thursday/Friday’s test on atomic
structure.
Objective
 I can use my understanding of
Unit 2- Atomic Structure to
complete the Unit 2 Test Review
Guide
Homework
 Unit 2 Study Guide
Agenda
1. Do Now, Objective (7 min)
2. Self-Assessment Check (5 min)
3. Unit 2 Study Guide Independent Practice
Time
1. Individual work station
2. Partner work station
3. Small group work station
Self-Assessment
 Look at how you assessed yourself for Unit 2
Concepts earlier in the week.
 Where do you think your understanding is
now?
 What do you want help from Ms. B with?
 What do you think you can do by yourself?
 What do you think you can do in a small
group?
 What do you think you can do with a
partner?
Independent Work Time
 You have 3 options today
 Individual work time – you can do all of the
study guide by yourself
 Partner Work – you can finish the study guide
working with 1 partner, you don’t need help
other than from each other
 Small Group – you aren’t sure if you can do
all the work. You want to work at stations with
other people, and get help from Ms. B
throughout the class
Independent Work Time
 Get your materials and go to where you
would like to work
 Expectations
 No phones
 No small talk/off-topic discussions
 Ask for help RIGHT AWAY when you need it –
from Ms. B, a friend, the textbook