To compare isotopes
Science - Atomic Structures
Mr Inder
Key principles
The I do phase involves the explanation - indicates where a teacher would be explaining and modelling a concept.
Moving from I do to We do involves guided practice - moving from teacher-led instruction to student-led practice.
Check for Understanding - Formative instruction questions, posed to check whether students have understood and to inform next instructional steps.
You do - Practice - indicates places where students will attempt questions independently.
At the expected level for the lesson; all students should be able to do these questions.
A small increase in difficulty from the expected level, eg larger numbers or a more complex calculation.
Extension - increased difficulty; suitable for a small number of students.
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I
CfU
W
Y
Support - support materials, such as additional templates or questions with fewer steps.
Engagement icons - to go in top right corner
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Whiteboard response
All students respond to the teacher’s question, showing their responses at the same time.
Non-volunteers
The teacher asks a question, gives wait time, then calls on individual students to respond.
Written response
Students respond to a prompt in a template, their exercise book or booklet.
Pair share
Students discuss with the person next to them.
Choral response
Students respond orally all together.
Thumbs up, thumbs down
Students indicate whether they agree or disagree with a statement, or whether something is an example or non-example.
Concrete materials
Teacher might choose to illustrate this teaching point using concrete materials.
Class discussion or activity
Students discuss as a class and share ideas
Calculator
Students will need a calculator to perform the task on this slide.
Spreadsheet
Students will need access to spreadsheet software to perform the task on this slide.
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In this lesson, you will need:
Exercise book or paper
Pen
Image credit: Pixabay
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In this lesson, you will need:
Calculator
Image credit: Pixabay
Periodic Table
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Starter Quiz
Isotopes
RAM Calculations
Worksheet
Exit Quiz
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In this lesson we will:
Keywords
Isotope: Variations of the same element, which differ based on mass
Atomic Mass: The mass of any particular atom
Relative Atomic Mass: The average mass of a sample of atoms
Abundance: The quantity of something present in a sample
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Isotopes
What you have learned so far about atoms
Atoms contain protons (+), neutrons (0) and electrons (-).
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The reality about neutrons
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1-Hydrogen�(Protium)
2-Hydrogen�(Deuterium)
3-Hydrogen�(Tritium)
+
0
+
0
0
+
Isotopes
*Not to scale!
Drawing and labelling isotopes
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Carbon-12
Carbon-13
Carbon-14
Draw and provide the atomic number and mass number for these isotopes:
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Oxygen-16
Oxygen-17
Oxygen-18
8 protons
8 protons
8 protons
8 neutrons
9 neutrons
10 neutrons
Y
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Relative Atomic Mass
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Relative Atomic Mass & Abundance
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1-Hydrogen�(Protium)
2-Hydrogen�(Deuterium)
3-Hydrogen�(Tritium)
+
0
+
0
0
+
Relative Abundance = 99.98%
Relative Abundance = 0.02%
Relative Atomic Mass & Abundance
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1-Hydrogen�(Protium)
2-Hydrogen�(Deuterium)
3-Hydrogen�(Tritium)
99.98%
0.12%
0.00%
99.98/100 x 1 = 0.9998
0.12/100 x 2 = 0.0024
0/100 x 3 = 0.0000
0.9998 + 0.0024 + 0.0000 = 1.0022 uamu
unified atomic mass unit
Your turn:�Boron has two isotopes, which occur in natural relative abundances as per the information below. Calculate the relative atomic mass of boron.
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Your turn:�Boron has two isotopes, which occur in natural relative abundances as per the information below. Calculate the relative atomic mass of boron.
Boron-10: 19.9%
Boron-11: 80.1%
19.9/100 x 10 = 1.99
80.1/100 x 11 = 8.811
1.99 + 8.811 = 10.801 uamu
Y
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Decimal Places
Our last example:
Boron-10: 19.9%
Boron-11: 80.1%
19.9/100 x 10 = 1.99
80.1/100 x 11 = 8.811
1.99 + 8.811 = 10.801 uamu
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1 d.p.
3 d.p.
Round to two decimal places?
Find the number and look next door
Five or above, add one more
Numbers in front stay the same
Numbers behind, zeroes remain
Our last example:
Boron-10: 19.9%
Boron-11: 80.1%
19.9/100 x 10 = 1.99
80.1/100 x 11 = 8.811
1.99 + 8.811 = 10.80 uamu
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1 d.p.
2 d.p.
Your turn:�A sample of magnesium was tested and shown to contain the following isotopes in abundance listed below. Calculate the relative atomic mass of magnesium in the sample and round to two decimal places.
Magnesium-24: 78.20%
Magnesium-25: 10.11%
Magnesium-26: 11.69%
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Y
Your turn:�A sample of magnesium was tested and shown to contain the following isotopes in abundance listed below. Calculate the relative atomic mass of magnesium in the sample and round to two decimal places.
Magnesium-24: 78.20%
Magnesium-25: 10.11%
Magnesium-26: 11.69%
78.20/100 x 24 = 18.768
10.11/100 x 25 = 2.5275
18.768 + 2.5275 + 3.0394 �= 24.3349 uamu
11.69/100 x 26 = 3.0394
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Your turn:�A sample of magnesium was tested and shown to contain the following isotopes in abundance listed below. Calculate the relative atomic mass of magnesium in the sample and round to two decimal places.
Magnesium-24: 78.20%
Magnesium-25: 10.11%
Magnesium-26: 11.69%
78.20/100 x 24 = 18.768
10.11/100 x 25 = 2.5275
18.768 + 2.5275 + 3.0394 �= 24.33 uamu (2 d.p)
11.69/100 x 26 = 3.0394
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Y
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Significant Figures
Example:�How many significant figures in each number?
2.183
4.21
9.3713
20.14
0.00082
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4 sig figs
3 sig figs
5 sig figs
4 sig figs
2 sig figs
Your turn:�How many significant figures in each number?
3.25
16.6894
4.032
0.0043
0.09082
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3 sig figs
6 sig figs
4 sig figs
2 sig figs
4 sig figs
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Our previous example:
Significant figures: �All numbers following the first non-zero digit.
Magnesium-24: 78.20%
Magnesium-25: 10.11%
Magnesium-26: 11.69%
78.20/100 x 24 = 18.768
10.11/100 x 25 = 2.5275
18.768 + 2.5275 + 3.0394 �= 24.3349 uamu
11.69/100 x 26 = 3.0394
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4 sig figs
5 sig figs
5 sig figs
5 sig figs
6 sig figs
Our previous example:
Magnesium-24: 78.20%
Magnesium-25: 10.11%
Magnesium-26: 11.69%
78.20/100 x 24 = 18.768
10.11/100 x 25 = 2.5275
18.768 + 2.5275 + 3.0394 �= 24.33 uamu
11.69/100 x 26 = 3.0394
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4 sig figs
5 sig figs
5 sig figs
5 sig figs
4 sig figs
Your turn:�A sample of lithium contains two isotopes - Lithium-6 (6.85% abundance) and Lithium-7 (93.15% abundance).�Calculate the relative atomic mass of lithium in the sample to the appropriate number of significant figures.
Lithium-6: 6.85%
Lithium-7: 93.15%
6.85/100 x 6 = 0.411
93.15/100 x 7 = 6.5205
0.411 + 6.5205�= 6.9315 uamu
3 sig figs
4 sig figs
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Y
Your turn:�A sample of lithium contains two isotopes - Lithium-6 (6.85% abundance) and Lithium-7 (93.15% abundance).�Calculate the relative atomic mass of lithium in the sample to the appropriate number of significant figures.
Lithium-6: 6.85%
Lithium-7: 93.15%
6.85/100 x 6 = 0.411
93.15/100 x 7 = 6.5205
0.411 + 6.5205�= 6.93 uamu
3 sig figs
4 sig figs
3 sig figs
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To compare isotopes
Complete the questions in the worksheet.
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Answers
a)
b)
c)
Nitrogen-14
Boron-10
Beryllium-7
Drawing must contain 5 protons and 9 neutrons
Drawing must contain 4 protons and 6 neutrons
Drawing must contain 3 protons and 4 neutrons
e.g.
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79 x 50.7/100 = 40.053
80 x 49.3/100 = 39.44
40.053 + 39.44 = 79.493
= 79.5 uamu (1 d.p.)
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12 x 98/100 = 11.76
13 x 1.5/100 = 0.195
14 x 0.50/100 = 0.07
11.76 + 0.197 + 0.07 = 12.027
All original values: 2 sig figs
=12 (2 sig figs)
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In this lesson we will:
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